Slide 1

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 2

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 3

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 4

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 5

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 6

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 7

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 8

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 9

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 10

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 11

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 12

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 13

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 14

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 15

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 16

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 17

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 18

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 19

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 20

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 21

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 22

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 23

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 24

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 25

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 26

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 27

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 28

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 29

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 30

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 31

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 32

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 33

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 34

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 35

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 36

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 37

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 38

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 39

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 40

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 41

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 42

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 43

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 44

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 45

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 46

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 47

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 48

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 49

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 50

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 51

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 52

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 53

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 54

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 55

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 56

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 57

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 58

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 59

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 60

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 61

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 62

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor


Slide 63

 Cooling

system functions
 Cooling system operation
 Cooling system types
 Basic cooling system
 Closed and open cooling systems
 Cooling system instrumentation
 Antifreeze
 Block heater

Cooling System Functions
Helps Engine Reach Operating Temperature Quickly
 Maintains Constant Engine Operating Temperature
 Removes Excess Engine Heat
 Provides Heat For Warming the Passenger Area


Helps Engine Reach Operating
Temperature Quickly
 Advantages

of Rapid Engine Warm-up:

Improved combustion
(better fuel vaporization)
Reduced part wear
Less oil contamination
Increased fuel economy
Reduced emissions

Advantages of Maintaining a
Proper Operating Temperature
Ensures

Proper Combustion
Minimum Emissions
Maximum Performance
Maintains Optimum Fuel Economy

© Goodheart-Willcox Co., Inc.

Maintains Constant
Operating Temperature
 Thermostat

opens and closes to Maintain Temp
 160 ºF to 195 ºF (Depending on thermostat)
 When an engine warms to operating
temperature parts expand and rapid warm-up
reduces part wear
 Ensures that clearances are correct

Removes Excess Engine Heat
On Modern Vehicles, Typical Combustion
Temperatures can reach 4500 ºF (2500 ºC)
 This is hot enough to melt metal parts
 Cooling system removes excess heat which can
cause major engine damage!


Air-cooled Engine




This air-cooled engine has had the cooling fan and
shrouding removed for better viewing.
The shrouding directs the air-flow around the cylinders

© Goodheart-Willcox Co., Inc.

 Two

common types:

air cooling

Cooling Fan & Shrouding
Removed for better view

liquid cooling

Air Cooling Versus
Liquid Cooling

Air Cooling Systems






Large cylinder cooling fins and outside air remove excess heat
Cooling fins increase the surface area of the metal around the
cylinder
This allows enough heat transfer to the outside air
Plastic or metal shrouds duct air onto and around the cylinder fins

Liquid Cooling Systems







Circulate coolant through the water jackets
Combustion heat is transferred to the coolant
Cooling system carries it out of the engine
Hot coolant flows into the radiator where heat is removed
Cooled coolant flows back into engine to repeat this process

Liquid Cooling Advantages
 Precise

temperature control
 Less temperature variation
 Reduced emissions
 Improved heater operation

Liquid Cooling
Heat is transferred to cylinder wall, into
coolant and carried away

Conventional Coolant Flow
 Hot

coolant flows from the cylinder head
to the radiator
 After being cooled in the radiator, the
coolant flows back into the engine block

Reverse Flow Cooling
 Cool

coolant enters the head and hot coolant
exits the block to return to the radiator
 Helps keep a more uniform temperature
throughout the engine
 Found on high-performance engines

 Components:

Radiator
Radiator Hoses
Fan
Thermostat
Water Pump

Radiator
Transfers coolant heat to the outside air

Radiator Types

Vertical Flow

Cross Flow

Radiator Hoses and
Heater Hoses

Hoses
 Radiator

Hoses

Carry coolant between the engine water
jackets and the radiator
Lower hose is exposed to water pump
suction so a spring may prevent collapse
 Heater

Hoses

Carry hot coolant to the heater core
Smaller diameter than radiator hoses

Hose Clamps
Three basic types of hose clamps

Radiator Hoses
Two basic types of radiator hoses

Radiator Fan

 Draws

air through the radiator and cools
off the hot coolant passing through it.

© Goodheart-Willcox Co., Inc.

Thermostat
 Maintains

a constant engine temperature
 Helps engine reach operating temperature
quickly
 Senses coolant temperature and controls
coolant flow through the radiator
 Reduces coolant flow on cold engine
 Increases coolant flow on hot engine

Thermostat
A temperature-sensitive valve

Thermostat Operation
 Cold

engine

wax-filled pellet has contracted
spring holds valve closed
 Hot

engine

when heated, pellet expands
spring tension is overcome
valve opens

Thermostat Operation

A. Cold engine
B. Hot engine

Thermostat Operation
Cold engine

Hot engine

Water Pump
A ribbed belt powers this pump which
pumps coolant throughout the engine.

Crank
pulley
Impeller

Ribbed
belt
Water
pump
pulley

Impeller Pump
Coolant is thrown outward by centrifugal force,
producing suction in the center of the pump housing.
Straight impeller blades use less energy to operate.

Water Pump Cutaway
Water Pump Parts

Radiator Types

Vertical Flow

Cross Flow

Tanks on top
and bottom

Tanks on both sides

Transmission Oil
Cooler
 Often

placed in the radiator on cars with
automatic transmissions
 Prevents transmission fluid from
overheating

Transmission Oil
Cooler
Small tank inside
one of the
radiator tanks

Water Pump Parts








Water pump housing -Iron or aluminum casting that
forms the main body of the pump.
Water pump impeller -Disk with fan-like blades, the
impeller spins and produces pressure and flow.
Water pump shaft -Steel shaft that transmits the
turning force from the hub to the impeller.
Water pump seal -Prevents coolant leakage between
pump shaft and pump housing.
Water pump bearing -Plain or ball-bearings that allow the
pump shaft to spin freely in housing.
Water pump gasket -Fits between the water pump and
the engine to prevent leakage.
Water pump hub -Provides a mounting place for the
belt, pulley, and fan.

Radiator Hoses and Clamps








Radiator hoses –Carry coolant between the engine water
jackets and the radiator.
Flexible hose –Has an accordion shape and can be bent to
different angles.
Molded hose –Manufactured in a special shape, with bends
to clear the cooling fan and other parts.
Heater hoses –Small-diameter hoses that carry coolant to
the heater core.
Hose spring –Frequently used in the lower radiator hose to
prevent the hose from collapsing.
Worm-drive hose clamps –Uses a worm gear that engages
slots in the clamp strap to allow tightening around the hose.
Hose clamps –Hold the radiator hoses and heater hoses
onto their fittings

Radiator Cap
 Seals

the radiator
 Pressurizes the system
 Relieves excess pressure
 Allows coolant flow between the
radiator and the coolant reservoir

Radiator Cap

Radiator Cap
Vacuum Valve
Opens to allow flow back into the radiator when the coolant
temperature drops. Without this valve the coolant would
not flow back into the radiator and the radiator would
become low on coolant and the engine would overheat.

Radiator Cap Pressure Valve
 Spring-loaded

disk
 Normally, water boils at 212 ºF (100 ºC)
 For each pound of pressure increase,
boiling point goes up about 3 ºF (1.6 ºC)
 Typical pressure:
12–16 psi
raises boiling point to
250–260 ºF (121–127 ºC)

 Closed

cooling system

Uses an Expansion Tank
Overflow tube is routed into reservoir tank
 Open

cooling system

Allows excess coolant to leak onto the ground

Pressure Cap
Operation
Hot engine

Cold engine

Cooling System Fans
 Pull

air through the core of the radiator
 Increase volume of air through the
radiator
 Driven by fan belt or electric motor

Flex Fan
High rpm cause blades to flex,
reducing blowing action

Fluid Coupling
Fan Clutch
Filled with
silicone-based oil
Slips at higher rpm

Thermostatic
Fan Clutch

 Bimetal

spring controls clutching action

Cold—clutch slips
Hot—clutch locks

Electric Cooling Fans








Provide cooling with an electric motor and a thermostatic switch
Use A small direct current motor to operate the cooling fan
Common on transverse-mounted engines
Save energy and increase cooling efficiency
Fans only function when needed

Electric Fan Operation
Cold engine
Hot engine

PCM-Controlled Fans
 When

cold, ECM does not energize fan relays
 After warm-up, ECM feeds current to the fan
relay coils, closing relay contacts
 High current flows to fans

Radiator Shroud
Ensures that the fan
pulls air through
the radiator core

Modern Cooling Systems
Use thermostats that are 195°F and higher
(which is higher than older vehicles, 160°F-180°F)

Advantages
Engines that run higher coolant temperatures:
 run smoother with more power
 run more efficiently and use less fuel
 burn much cleaner
 heaters/defrosters work better

Thermostat Operation
Cold engine – Thermostat is closed no
coolant flows through the radiator

Bypass Valve
Permits some circulation
through the engine when
the thermostat is closed

Bypass Thermostat
Blocks off the bypass at operating
temperature
Impeller
Flow to
radiator
Water pump
drive pulley

Water pump
housing

Bypass
spring

Bypass
flow
Thermostat
Main
spring
Main flow

Thermostat Jiggle Valve



The valve allows trapped air to escape when the cooling system is flushed
or opened for repairs. The trapped air is a serious problem which could
prevent the thermostat from opening and create hot spots with erratic sensor
behavior. The air is hard to remove without the valve. Since air rises up in
water, the valve should be installed in the 12 o'clock position.

Temperature Warning Light
 When

coolant becomes too hot, a
temperature sending unit (switch) in the
block closes, completing a circuit
and the warning light comes on, letting the
driver know there is a problem.

Warning Light Circuit

Composed of ethylene glycol mixed with water

Prevents winter freeze-up
 Prevents rust and corrosion
 Lubricates the water pump
 Raises the boiling point
 Lowers the freezing point


Antifreeze/Water Mixture
A 50/50 mixture is most commonly used

50% ANTFREEZE
50% WATER

Lowers coolant freezing point to -34 ºF
Raises the boiling point to 265 ºF

Corrosion Protection

Protected with
antifreeze

Water only

 Aids

engine starting in cold weather
 120-volt heating element mounted in the
block water jacket
 Common on diesel engines

Block Heater
Installation

Questions?
 Refer

to Duffy textbook chapter 39
 Scroll back through power-point
 Ask fellow student for help
 After following all the above steps,
check with your instructor