brake system diagnosis and repair chapter 72 - part two

Brake System Diagnosis and Brake System Diagnosis and Repair Repair

Chapter 72 - Part Two

Disc Brake Service Disc Brake Service

• A typical major disc brake service A typical major disc brake service involves four basic operations: involves four basic operations:

• Replacing worn brake padsReplacing worn brake pads• Rebuilding/replacing the calipersRebuilding/replacing the calipers• Machining the brake rotorsMachining the brake rotors• Flushing the brake fluidFlushing the brake fluid


The twelve steps for replacing worn disc brake pads are: 1. Loosen the wheel lug nuts


The twelve steps for replacing worn disc brake pads are: 2. Raise and secure the vehicle, remove the wheels


The twelve steps for replacing worn disc brake pads are: 3. Push the caliper pistons back into the caliper


The twelve steps for replacing worn disc brake pads are: 4. Unbolt and remove calipers

(With brake hose still attached)


The twelve steps for replacing worn disc brake pads are: 5. Hang calipers by a piece of wire (or bungee cord)


The twelve steps for replacing worn disc brake pads are: 6. Remove old brake pads from calipers


The twelve steps for replacing worn disc brake pads are: 7. Install anti-rattle clips on new pads


The twelve steps for replacing worn disc brake pads are: 8. Install the new pads into the calipers


The twelve steps for replacing worn disc brake pads are: 9. Clean, lube, and slide the caliper

assemblies over the brake discs


The twelve steps for replacing worn disc brake pads are: 10. Assemble the caliper mounting hardware

(reverse order of disassembly)


The twelve steps for replacing worn disc brake pads are: 11. Torque all bolts properly


The twelve steps for replacing worn disc brake pads are: 12. Install wheel and torque the lug nuts

Disc Brake Service - Disc Brake Service - Caliper Parts

Disc Brake Service - Disc Brake Service - CaliperCaliper

Caution!Caution! You can crush your finger when using compressed air to remove a caliper piston during rebuilding.

Disc Brake Service - Disc Brake Service - CaliperCaliper• 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 - Disc Brake Service - CaliperCaliper• You should use a pointed hook tool to remove

the caliper piston seal.

Disc Brake Service – Disc Brake Service – Disc/RotorDisc/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 Brake Service – Disc/RotorDisc/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 Brake Service – Disc/RotorDisc/Rotor• The warpage or brake disc runout typically

should not exceed 0.004”

Disc Brake Service – Disc Brake Service – Disc/RotorDisc/Rotor

Brake Lathe for machining Disc/Rotors off the vehicle


On-the-Car Brake Lathe for machining Disc/Rotors on the vehicle.

(You don’t have to remove the disc to machine it!)


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 ServiceDrum 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 - Drum Brake Service - ToolsTools

Drum Micrometer Brake Cylinder Hone Spring Depressor Pressure Bleeder

Micrometer Bleeder Wrench Brake Spring Pliers Dial Indicator

Drum Brake ServiceDrum Brake Service

• 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 - PartsDrum Brake Service - Parts

Drum Brake Service - TipsDrum Brake Service - Tips

Some good methods of remembering how Some good methods of remembering how the rear drum brake parts go together: the rear drum brake parts go together: Taking a digital picture Taking a digital picture Taking only one side apart at a time Taking only one side apart at a time Making a drawing Making a drawing

If a brake drum’s inside diameter is too big If a brake drum’s inside diameter is too big the drum must be replaced. the drum must be replaced.

The preparation of the brake drum’s inner surface The preparation of the brake drum’s inner surface is called machining, turning, or resurfacing is called machining, turning, or resurfacing

Drum Brake Service - TipsDrum Brake Service - Tips

Brake shoe linings are fastened to the Brake shoe linings are fastened to the brake shoe by rivets, glue, or both.brake shoe by rivets, glue, or both.

Lubricating of the backing plate should be done Lubricating of the backing plate should be done with high temp grease, sparingly. with high temp grease, sparingly.

Parking brakes should never be adjusted too tight. Parking brakes should never be adjusted too tight.

Parking brakes that are adjusted too tight can Parking brakes that are adjusted too tight can overheat, drag, or cause pulling.overheat, drag, or cause pulling.

QUESTIONS?

Check in the Duffy textbook Chapter 72

brake system diagnosis and repair chapter 72 - part two

Documents

brake disc runout

brake discrotor

worn disc brake pads

brake rotors

brake drums

brake hose

brake operation

brake shoes