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