Slide 1


Slide 2

(12 Topics)

Cooling system diagnosis
Cooling system problems
Water pump service
Thermostat service
Cooling system hose service
Radiator and pressure cap service


Slide 3

Fan belt service
Engine fan service
Freeze plug service
Coolant service
Flushing a cooling system
Temperature gauge service


Slide 4

 Gather information:
Talk to the owner or service writer to find out as
much as possible about the symptoms
A Cooling System Diagnosis Chart in the
service manual can be very helpful when
problems are difficult to locate and correct.


Slide 5

On-Board Diagnostics
Cooling-related problems may set a
diagnostic trouble code on some
systems if temperatures seem out of
range.
use a scan tool to analyze the system
MIL lamp may be on
data will indicate engine temperature
even failure to bleed a system of air could
cause erratic temperature sensing


Slide 6

Cooling System Functions
often monitored by the
OBD II system:
Coolant Temperature
Engine oil Temperature
Belt Tension
Other related functions


Slide 7

Visual Inspection of
Cooling System
Perform a visual inspection for:
coolant leaks
loose or missing fan belts
low coolant level
water pump noises
plugged radiator fins
coolant in the oil (oil looks milky)
combustion leakage into coolant


Slide 8

Common Problems


Slide 9

Coolant leaks
Overheating
Overcooling


Slide 10

Coolant Leaks
External leaks
most common
show up as wet, discolored areas on parts

Internal leaks
caused by cracked block, head or blown
head gasket


Slide 11

Cooling System
Problems
A blown head gasket
can allow combustion
gases to enter the
coolant, a combustion
leak test will verify this
type of problem


Slide 12

Cooling System
Problems
Mineral deposits in
water jackets can
prevent proper heat
transfer


Slide 13

Cooling System
Problems
A cracked part or
blown gasket can
allow coolant to leak
into the engine oil and
cause a milky white
substance to form in
the valve covers


Slide 14

Cooling System
Pressure Tester

One of the most commonly used and
important cooling system testing devices!


Slide 15

Cooling System
Pressure Test
TO AVOID SERIOUS BURNS, NEVER
REMOVE A RADIATOR CAP WHEN
ENGINE IS HOT!
Install pressure tester on filler neck
Pump the tester to pressurize system
Use cap rating for maximum psi to avoid serious
damage to cooling system

Low air pressure is forced into the system
causes coolant to pour or drip from any leak


Slide 16

Combustion Leak Test
 Should be performed when indications of a
blown head gasket, cracked head, or cracked
block are suspected.
 Checks for the presence of combustion gases
in the coolant
 Place combustion leak tester on filler neck
 Start engine and squeeze tester bulb, pulling air
through test fluid
 If combustion gases are present in the radiator,
fluid changes color (from blue to yellow)


Slide 17

Combustion Leak Test
Combustion leakage
can make
the engine overheat


Slide 18

Combustion Leak Test
Leak testing with an exhaust gas
analyzer. HC reading indicates leakage


Slide 19

Causes of Overheating
Low coolant level
Rust or scale accumulation in coolant
Stuck thermostat
Retarded ignition
Loose fan/water pump belt
Bad water pump
Collapsed lower hose
Missing fan shroud or fan problems
Ice in the coolant


Slide 20

Causes of
Overcooling
Stuck thermostat (open)
Locked fan clutch
Shorted fan switch

Indications of Overcooling
Heater does not get hot
Temperature gage remains cold
Poor fuel economy


Slide 21

A bad pump may leak, fail to circulate
coolant, or produce a grinding sound
Common Causes of Water Pump Failure:
rust in the cooling system
lack of coolant
overtightened belts


Slide 22

Visual Inspection
(Checking for worn Water Pump Bearings)

Pump shaft should not wiggle or leak


Slide 23

Visual Inspection

Watch for leakage from bleed holes
A mechanic’s stethoscope can be used to
pinpoint failing water pump bearings


Slide 24

Removing a Water
Pump
 Unbolt brackets and components
air-conditioning compressor
power steering pump
alternator

 Remove pump
 Scrape off old gasket or sealer material
 Do not use excessive force when separating
a water pump from an engine because you
may gouge the sealing surfaces!


Slide 25

Installing a New Water Pump
(Most Technicians prefer to install a new water pump rather
than rebuilding the old one, because it is more cost effective
and comes with a better warranty)
 Fit pump onto the engine
 Start all bolts by hand
 Torque all fasteners to specifications
 Use sealer where specified
 Install the other components


Slide 26

Installing a Water
Pump
A. Gasket held in place by sealer
B. Sealer only

Note: Be sure to use the correct sealer to adhere the water pump
gasket to the water pump to avoid coolant leakage


Slide 27

Water Pump

This pump uses an O-ring seal
instead of sealer or gasket


Slide 28

Installation
Tightening water
pump bolts evenly to
proper torque specs


Slide 29

Water Pump
Components


Slide 30

A stuck thermostat can cause engine
overheating or overcooling
Stuck open–overcooling
loss of efficiency, power, mileage
high emissions

Stuck closed–overheating
engine damage


Slide 31

Thermostat Testing
 Watch the coolant through the opening in the
radiator neck
 Cold engine, coolant should not flow
 Hot engine, coolant should begin to circulate past
the opening
 Use a digital thermometer to monitor the
temperature of the thermostat housing and outlet
hose. If the housing is reaching engine operating
temperature but the outlet hose stays cool, the
thermostat is not opening and needs to be replaced


Slide 32

Thermostat and
Housing

Caution: Over tightening the thermostat housing can
cause it to warp or crack and create coolant leakage


Slide 33

Thermostat
Replacement


Slide 34

Thermostat and Housing

Some manufacturers use an O-ring seal which should
be replaced anytime the thermostat is removed


Slide 35

Bleeding the Cooling System
A bleed valve is sometimes provided to help
eliminate trapped air in the cooling system
Cars with low hood lines require a bleed
screw to empty air pockets
Trapped air can cause overheating or a
buildup of heat called a hot spot


Slide 36

Bleeding the Cooling
System
Fill the system
Start and warm the engine
Crack open the bleed screw until all air
is purged from the system
Never remove a cooling system
bleed screw or any clamp on a hot,
pressurized system!


Slide 37

Hoses deteriorate and become
soft and mushy or hard and brittle
and should be replaced


Slide 38

Common
Hose
Problems


Slide 39

Hose Replacement
A.
B.
C.
D.
E.

Loosen clamp,
Twist and pull hose off
Clean fitting
Install new hose and clamp
Check for leaks


Slide 40


Slide 41

Inspecting the Radiator
and Pressure Cap
Conditions that can limit airflow through the radiator
 Inspect radiator fins for debris and rot
 Make sure the shroud is in place
 Perform a Radiator Cap Pressure Test
which measures cap opening pressure
checks sealing washer condition
TO AVOID SERIOUS BURNS, NEVER REMOVE
A RADIATOR CAP WHEN ENGINE IS HOT!


Slide 42

Pressure Testing a
Radiator Cap


Slide 43

Radiator Removal
Place a catch pan under the cool radiator
Open the petcock to drain system
Disconnect hoses and oil cooler lines
Disconnect wires going to sensors and
fan motors
Remove any brackets and radiator


Slide 44

Radiator Removal


Slide 45

Radiator Repair
Most repairs are done by a radiator shop
Radiator shops disassemble, clean, repair,
reassemble and test radiators
When installing radiator, make sure the
rubber mounts are in place


Slide 46

An over tightened fan/water pump belt
can cause water pump bearing failure
A loose fan belt will slip and squeal and
may cause overheating
Inspect the condition and tension
Use a belt tension gauge to adjust belts


Slide 47

A faulty fan can cause overheating,
overcooling, vibration and water pump
damage
Check for bent blades, cracks or fluid
leakage


Slide 48

Testing a
Thermostatic Fan Clutch
Start the engine
When cold, fan should slip
When warm, clutch should engage
you should hear the rush of air


Slide 49

Electric Cooling Fan

Most electric cooling system fans are controlled by a
temperature switch or sensor located in the radiator,
thermostat housing, or engine block.
When the engine is cold, the fan stays off, which saves on
fuel and helps the engine warm-up more quickly.
When the engine is warm the fan only comes on when
necessary, which also helps improve fuel economy.


Slide 50

Testing an Electric Cooling Fan

A. Check for power to the fan, engine hot
B. Switch open when cold, closed when hot
C. Test using a test lamp or digital volt meter


Slide 51

Leaking freeze plugs cause coolant
loss and overheating
Occasional replacement may be
necessary because of corrosion
Freeze plugs are made thinner than the
metal in the engine block and will fail
much sooner than other parts of the
engine


Slide 52

Freeze Plug
Replacement
A.
B.
C.
D.
E.

Drive drift through plug
Pry out
Clean hole
Coat hole with sealer
Install with driver tool


Slide 53

Coolant should be checked and changed at
regular intervals (according to manufacturer’s recommendations)
Breaks down and becomes conductive
Rust preventative properties are lost
Boiling and freezing properties may become
compromised.


Slide 54

Digital Volt Meter used to check for
dissolved metals in the coolant

Coolant Tester used to check the
boiling & freezing points of the coolant

One of the most common causes of cracked blocks and cylinder heads is
water freezing and expanding in the engine from lack of coolant!


Slide 55

Changing Coolant


Slide 56

Checking Coolant
Level
With recovery reservoir: Coolant should be even with correct
marking on reservoir and full to top of radiator

Full

Max
Min


Slide 57

Checking Coolant
Level
Without recovery
reservoir:
Coolant should be 1”
below the top
of the tank on systems
without a recovery tank


Slide 58

Testing Coolant
Strength
Measures the concentration of
antifreeze compared to water
Determines freeze protection
Tools used:
cooling system hydrometer
refractometer


Slide 59

Coolant Tester/Hydrometer
When filled, pointer will float to indicate
freeze protection


Slide 60

 Cleans rust and scale from the system.
 Rust (iron oxide) is very harmful to the cooling
system. It can cause premature failure of the
water pump, block small passages in the radiator
core, and cause electrolysis to occur.
 May involve running a cleaning chemical through
the system
 Methods:
fast flushing
reverse flushing
chemical flushing


Slide 61

Fast Flushing


Slide 62

Reverse
Flushing
Reverse flushing
involves flowing
air and water
backwards to the
normal flow of
coolant through
the radiator core
and engine block


Slide 63

Chemical Flushing
 Used when scale buildup is causing
overheating
 Chemical cleaner is added to the coolant
 Engine is operated for a specific amount of
time
 System is flushed with water


Slide 64

Gauge problems may include
the gauge reading too hot, too
cold, or not moving at all


Slide 65

Gauge or Indicator
Light Test
Disconnect wire from temperature
sending unit
Turn key on, ground wire
If gauge sweeps or light glows as wire
is grounded this indicates the gauge is
working. The sending unit may require
replacement
Check service manual before this test


Slide 66

Gauge Tester
Used if the gauge is suspected of being
faulty or out of calibration
Special device with a variable resistor,
replaces the temperature sending unit in
the temperature gauge circuit

Using Gauge Tester

Set tester to a specified resistance
Connect tester as in diagram on next slide
Gauge should read as specified


Slide 67

Gauge or Indicator
Light Test


Slide 68

Questions?
Refer to Duffy textbook chapter 40
Scroll back through power-point
Ask fellow student for help
After following all the above steps,
check with your instructor

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