Transcript Brake System Diagnosis and Repair Chapter 72 - Part Two Disc Brake Service • A typical major disc brake service involves four basic operations: •

Brake System Diagnosis and Repair
Chapter 72 - Part Two
Disc Brake Service
• A typical major disc brake service
involves four basic operations:
• Replacing worn brake pads
• Rebuilding/replacing the calipers
• Machining the brake rotors
• Flushing the brake fluid
Disc Brake Service
The twelve steps for replacing worn disc brake pads are:
1. Loosen the wheel lug nuts
Disc Brake Service
The twelve steps for replacing worn disc brake pads are:
2. Raise and secure the vehicle, remove the wheels
Disc Brake Service
The twelve steps for replacing worn disc brake pads are:
3. Push the caliper pistons back into the caliper
Disc Brake Service
The twelve steps for replacing worn disc brake pads are:
4. Unbolt and remove calipers
(With brake hose still attached)
Disc Brake Service
The twelve steps for replacing worn disc brake pads are:
5. Hang calipers by a piece of wire (or bungee cord)
Disc Brake Service
The twelve steps for replacing worn disc brake pads are:
6. Remove old brake pads from calipers
Disc Brake Service
The twelve steps for replacing worn disc brake pads are:
7. Install anti-rattle clips on new pads
Disc Brake Service
The twelve steps for replacing worn disc brake pads are:
8. Install the new pads into the calipers
Disc Brake Service
The twelve steps for replacing worn disc brake pads are:
9. Clean, lube, and slide the caliper
assemblies over the brake discs
Disc Brake Service
The twelve steps for replacing worn disc brake pads are:
10. Assemble the caliper mounting hardware
(reverse order of disassembly)
Disc Brake Service
The twelve steps for replacing worn disc brake pads are:
11. Torque all bolts properly
Disc Brake Service
The twelve steps for replacing worn disc brake pads are:
12. Install wheel and torque the lug nuts
Disc Brake Service - Caliper Parts
Disc Brake Service - Caliper
Caution!
You can crush your finger when using compressed air
to remove a caliper piston during rebuilding.
Disc Brake Service - Caliper
• You should use only brake cleaner or brake
fluid to clean brake caliper parts! Coating the
brake caliper piston with brake fluid before
installation helps to make reassembly go easier.
Disc Brake Service - Caliper
• You should use a pointed hook tool to remove
the caliper piston seal.
Disc Brake Service – Disc/Rotor
• The two most important precision measurements
that need to be made on a brake disc/rotor are
the disc thickness and the disc runout .
Measuring disc thickness
Measuring disc runout
Disc Brake Service – Disc/Rotor
• The minimum disc thickness is measured across the
two friction surfaces in several different places.
• The maximum disc runout is the amount of side-to-side
movement measured near the outer edge of the brake
disc’s friction surface.
Measuring disc thickness
Measuring disc runout
Disc Brake Service – Disc/Rotor
• The warpage or brake disc runout typically
should not exceed 0.004”
Disc Brake Service – Disc/Rotor
Brake Lathe
for machining Disc/Rotors off the vehicle
Disc Brake Service – Disc/Rotor
On-the-Car Brake Lathe
for machining Disc/Rotors on the vehicle.
(You don’t have to remove the disc to machine it!)
Disc Brake Service – Disc/Rotor
When machining a disc, you must do all the following:
1. Measure the disc before machining
2. Measure the disc after machining
3. Document the measurements on the repair order
Brake discs should be inspected for all of the following
defects:
1. Hot Spots
2. Cracks
3. Warpage
Drum Brake Service
• A typical Drum Brake Service includes these
seven operations:
• Remove parts from the backing plate
• Clean and inspect the parts
• Replace the brake shoes
• Replace or rebuild the wheel cylinders
• Turn the brake drums
• Lubricate and reassemble the brake parts
• Pre-adjust, bleed, and test the brakes
Drum Brake Service - Tools
Drum Micrometer
Brake Cylinder Hone
Micrometer
Bleeder Wrench
Spring Depressor
Brake Spring Pliers
Pressure Bleeder
Dial Indicator
Drum Brake Service
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Gently hammering on the brake drum can help loosen it.
Springs on drum brakes can be different colors.
Leaking wheel cylinders will affect brake operation.
Working on drum brakes requires many special tools.
When honing the wheel cylinder it is never a good idea
to pull the hone out of the cylinder while it is spinning or
you may cause damage to yourself, the hone, or the
wheel cylinder!
Drum Brake Service - Parts
Drum Brake Service - Tips
Some good methods of remembering how
the rear drum brake parts go together:
Taking a digital picture
Taking only one side apart at a time
Making a drawing
If a brake drum’s inside diameter is too big
the drum must be replaced.
The preparation of the brake drum’s inner surface
is called machining, turning, or resurfacing
Drum Brake Service - Tips
Brake shoe linings are fastened to the
brake shoe by rivets, glue, or both.
Lubricating of the backing plate should be done
with high temp grease, sparingly.
Parking brakes should never be adjusted too tight.
Parking brakes that are adjusted too tight can
overheat, drag, or cause pulling.
QUESTIONS?
• SEE INSTRUCTOR