Hummer H2. Manual — part 777

wheel assembly rotation.

Disc Brake Pad Hardware

Secures disc brake pads firmly in proper relationship to the hydraulic brake calipers and enables a sliding
motion of brake pads when mechanical output force is applied.

Disc Brake Caliper Hardware

Provides mounting for hydraulic brake caliper and secures the caliper firmly in proper relationship to caliper
bracket. Enables a sliding motion of the brake caliper to the brake pads when mechanical output force is
applied.

DISC BRAKE SYSTEM OPERATION

Mechanical output force is applied from the hydraulic brake caliper pistons to the inner brake pads. As the
pistons press the inner brake pads outward, the caliper housings draw the outer brake pads inward. This allows
the output force to be equally distributed. The brake pads apply the output force to the friction surfaces on both
sides of the brake rotors, which slows the rotation of the tire and wheel assemblies. The correct function of both
the brake pad and brake caliper hardware is essential for even distribution of braking force.

PARK BRAKE SYSTEM DESCRIPTION

Park Brake Pedal Assembly

Releases applied park brake system when pulled.

Park Brake Cables

Transfers input force received from park brake pedal, through park brake cable equalizer, to park brake apply
lever.

Park Brake Cable Equalizer

Evenly distributes input force to both the left and right park brake units. Threaded park brake cable equalizers
are also used to remove slack in park brake cables.

Park Brake Apply Lever

Multiplies and transfers input force to park brake actuator/adjuster.

Park Brake Actuator/Adjuster

Uses multiplied input force from apply lever to expand park brake shoe (rear disc, drum-in-hat system), or drum
brake shoes toward the friction surface of the drum-in-hat of the rear brake rotor, or the brake drum. Threaded
park brake actuators/adjusters are also used to control clearance between the park brake shoe (rear disc, drum-
in-hat system), or the drum brake shoes and the friction surface of the drum-in-hat (of the rear brake rotor), or

2004 Hummer H2

2003-04 BRAKES Disc - Hummer

the brake drum.

Park Brake Shoe

Applies mechanical output force from park brake actuator to friction surface of the drum-in-hat portion of the
rear brake rotor.

PARK BRAKE SYSTEM OPERATION

Park brake apply input force is received by the park brake pedal assembly being depressed, transferred and
evenly distributed, through the park brake cables and the park brake cable equalizer, to the left and right park
brake apply levers. The park brake apply levers multiply and transfer the apply input force to the park brake
actuators/adjusters which expand the park brake shoe (rear disc, drum-in-hat system), or the drum brake shoes
toward the friction surface of the drum-in-hat (of the rear brake rotor), or the brake drum in order to prevent the
rotation of the rear tire and wheel assemblies. The park brake pedal assembly releases an applied park brake
system when it is depressed again.

BLEEDING BRAKE SYSTEM

BRAKE BLEEDING SEQUENCE

BRAKE BLEEDING SEQUENCE

MASTER CYLINDER BENCH BLEEDING

Application

Sequence

H2

RR, LR, RF, LF

WARNING:

Brake fluid may irritate eyes and skin. In case of eye contact, rinse
thoroughly with water. In case of skin contact, wash with soap and water.
In case of ingestion, consult a physician immediately.

CAUTION: Avoid spilling brake fluid onto painted surfaces, electrical connections,

wiring, or cables. Brake fluid will damage painted surfaces and cause
corrosion to electrical components. If any brake fluid comes in contact
with painted surfaces, immediately flush the area with water. If any brake
fluid comes in contact with electrical connections, wiring, or cables, use a
clean shop cloth to wipe away the fluid.

CAUTION: When adding fluid to the brake master cylinder reservoir, use only Delco

Supreme 11(R) (GM P/N 12377967), or equivalent DOT-3 brake fluid from a
clean, sealed brake fluid container. The use of any type of fluid other than
the recommended type of brake fluid, may cause contamination which
could result in damage to the internal rubber seals and/or rubber linings of
hydraulic brake system components.

2004 Hummer H2

2003-04 BRAKES Disc - Hummer

1. Secure the mounting flange of the brake master cylinder in a bench vise so that the rear of the primary

piston is accessible. See Fig. 1 .

2. Remove the master cylinder reservoir cap and diaphragm.

3. Install suitable fittings to the master cylinder ports that match the type of flare seat required and also

provide for hose attachment.

4. Install transparent hoses to the fittings installed to the master cylinder ports, then route the hoses into the

master cylinder reservoir.

5. Fill the master cylinder reservoir to at least the half-way point with Delco Supreme 11(R) (GM P/N

12377967), or equivalent DOT-3 brake fluid from a clean, sealed brake fluid container.

6. Ensure that the ends of the transparent hoses running into the master cylinder reservoir are fully

submerged in the brake fluid.

7. Using a smooth, round-ended tool, depress and release the primary piston as far as it will travel, a depth

of about 1" (25 mm), several times. Observe the flow of fluid coming from the ports. As air is bled from
the primary and secondary pistons, the effort required to depress the primary piston will increase and the
amount of travel will decrease.

8. Continue to depress and release the primary piston until fluid flows freely from the ports with no

evidence of air bubbles.

9. Remove the transparent hoses from the master cylinder reservoir.

10. Install the master cylinder reservoir cap and diaphragm.

11. Remove the fittings with the transparent hoses from the master cylinder ports. Wrap the master cylinder

with a clean shop cloth to prevent brake fluid spills.

12. Remove the master cylinder from the vise.

2004 Hummer H2

2003-04 BRAKES Disc - Hummer

Fig. 1: Accessing Rear Of Primary Piston
Courtesy of GENERAL MOTORS CORP.

MANUAL BLEEDING

WARNING:

Brake fluid may irritate eyes and skin. In case of eye contact, rinse
thoroughly with water. In case of skin contact, wash with soap and water.
In case of ingestion, consult a physician immediately.

CAUTION: Avoid spilling brake fluid onto painted surfaces, electrical connections,

wiring, or cables. Brake fluid will damage painted surfaces and cause
corrosion to electrical components. If any brake fluid comes in contact
with painted surfaces, immediately flush the area with water. If any brake
fluid comes in contact with electrical connections, wiring, or cables, use a
clean shop cloth to wipe away the fluid.

2004 Hummer H2

2003-04 BRAKES Disc - Hummer