Hummer H2. Manual — part 789

6. Inspect the disc brake system for proper operation. See DISC BRAKE SYSTEM DIAGNOSIS under

TROUBLE SHOOTING. If the condition was found and corrected, go to step 8 . If the condition was not
found and corrected, go to step 7 .

7. Inspect the brake assist system for proper operation. If the condition was found and corrected, go to step

8 . If the condition was not found and corrected, go to DIAGNOSTIC STARTING POINTS under
TROUBLE SHOOTING.

8. Road test the vehicle to confirm proper operation. See BRAKE SYSTEM VEHICLE ROAD TEST

under SYSTEM TESTS. If the condition is still present, go to step 2 . If the condition is not present,
system is okay.

BRAKE PEDAL EXCESSIVE EFFORT

1. If you were sent here from General Diagnosis, go to step 2 . If you were not sent here from General

Diagnosis, see DIAGNOSTIC STARTING POINTS under TROUBLE SHOOTING.

2. Inspect the brake assist system for proper operation. If the condition was found and corrected, go step 5 .

If the condition was not found and corrected, go step 3 .

3. Inspect the hydraulic brake system for proper operation. See HYDRAULIC BRAKE SYSTEM

DIAGNOSIS under TROUBLE SHOOTING. If the condition was found and corrected, go to step 5 . If
the condition is not found and corrected, go to step 4 .

4. Inspect the disc brake system for proper operation. See DISC BRAKE SYSTEM DIAGNOSIS under

TROUBLE SHOOTING. If the condition was found and corrected, go to step 5 . If the condition was not
found and corrected, see DIAGNOSTIC STARTING POINTS under TROUBLE SHOOTING.

5. Road test the vehicle to confirm proper operation. See BRAKE SYSTEM VEHICLE ROAD TEST

under SYSTEM TESTS. If the condition is still present, go to step 2 . If the condition is not present,
system is okay.

BRAKES DRAG

1. If you were sent here from General Diagnosis, go to step 2 . If you were not sent here from General

Diagnosis, see DIAGNOSTIC STARTING POINTS under TROUBLE SHOOTING.

2. If the vehicle is equipped with an adjustable stop light switch and/or an adjustable cruise control release

switch, go to step 3 . If the vehicle is not equipped with an adjustable stop light switch and/or an
adjustable cruise control release switch, go to step 4 .

3.

z

Inspect the stop light switch for proper adjustment to ensure that the brake pedal is fully releasing.

z

Inspect the cruise control release switch, if equipped, for proper adjustment to ensure that the brake
pedal is fully releasing.

If the condition was found and corrected, go to step 11 If the condition was not found and corrected, go to
step 4 .

4. Inspect the park brake system for proper operation. See PARK BRAKE SYSTEM DIAGNOSIS under

TROUBLE SHOOTING. If the condition was found and corrected go to step 11 . If the condition was not
found and corrected, go to step 5 .

5. Inspect the disc brake system for proper operation. See DISC BRAKE SYSTEM DIAGNOSIS under

2004 Hummer H2

2003-04 BRAKES Disc - Hummer

TROUBLE SHOOTING. If the condition was found and corrected, go to step 11 . If the condition was
not found and corrected, go to step 6 .

6. Separate the brake booster pushrod from the brake pedal. Inspect the brake corners to determine if the

brake drag condition is still present. If the brake corners still exhibit the brake drag condition, go to step
8 . If the brake corners DO NOT exhibit the brake drag condition, go to step 7 .

7. Replace the brake pedal assembly. If the replacement has been completed, go to step 11 .

8.

A. Separate the master cylinder from the brake booster. DO NOT disconnect any brake pipes.

B. Inspect the brake corners to determine if the brake drag condition is still present.

If the brake corners still exhibit the brake drag condition, go to step 10 . If the brake corners DO NOT
exhibit the brake drag condition, go to step 9 .

9. Replace the brake booster assembly. See BRAKE BOOSTER under REMOVAL & INSTALLATION.

After repairs are complete, go to step 11 .

10. Inspect the hydraulic brake system for proper operation. See HYDRAULIC BRAKE SYSTEM

DIAGNOSIS under TROUBLE SHOOTING. If the condition was found and corrected, go to step 11 . If
the condition was not found and corrected, see HYDRAULIC BRAKE SYSTEM under DIAGNOSTIC
STARTING POINTS in TROUBLE SHOOTING.

11. Install or connect components that were removed or disconnected during diagnosis. Road test the vehicle

in order to confirm proper operation. See BRAKE SYSTEM VEHICLE ROAD TEST under SYSTEM
TESTS. If the condition is still present, go to step 2 . If the condition is not present, system okay.

BRAKE SYSTEM SLOW RELEASE

1. If you were sent here from General Diagnosis, go to step 2 . If you were not sent here from General

Diagnosis, see DIAGNOSTIC STARTING POINTS under TROUBLE SHOOTING.

2. Inspect the hydraulic brake system for proper operation. See HYDRAULIC BRAKE SYSTEM

DIAGNOSIS under TROUBLE SHOOTING. If the condition was found and corrected, go to step 5 . If
the condition was not found and corrected, go to step 3 .

3. Inspect the brake assist system for proper operation. If the condition was found and corrected, go to step

5 . If the condition was not found and corrected, go to step 4 .

4. Inspect the disc brake system for proper operation. See DISC BRAKE SYSTEM DIAGNOSIS under

TROUBLE SHOOTING. If the condition was found and corrected, go to step 5 . If the condition was not
found and corrected, go to DIAGNOSTIC STARTING POINTS under TROUBLE SHOOTING.

5. Road test the vehicle to confirm proper operation. See BRAKE SYSTEM VEHICLE ROAD TEST

under SYSTEM TESTS. If the condition is still present, go to step 2 . If the condition is not present,
system is okay.

BRAKE FLUID LOSS

1. If you were sent here from General Diagnosis, go to step 2 . If you were not sent here from General

Diagnosis, see DIAGNOSTIC STARTING POINTS under TROUBLE SHOOTING.

2. Inspect the hydraulic brake system for proper operation. See HYDRAULIC BRAKE SYSTEM

DIAGNOSIS under TROUBLE SHOOTING. If the condition was found and corrected, go to step 4 . If

2004 Hummer H2

2003-04 BRAKES Disc - Hummer

the condition was not found, go to step 3 .

3. Inspect the disc brake system for proper operation. See DISC BRAKE SYSTEM DIAGNOSIS under

TROUBLE SHOOTING. If the condition was found and corrected, go to step 4 . If the condition was not
found and corrected, go to step 4 .

4. Road test the vehicle to confirm proper operation. See BRAKE SYSTEM VEHICLE ROAD TEST

under SYSTEM TESTS. If the condition is still present, go to step 2 . If the condition is not present,
system is okay.

BRAKES SELF APPLY WHEN TURNING STEERING WHEEL

1. If you were sent here from General Diagnosis go to step 2 . If you were not sent here from General

Diagnosis, see DIAGNOSTIC STARTING POINTS under TROUBLE SHOOTING.

2. Inspect the steering system for proper operation. See appropriate POWER RECIRCULATING BALL

article. If the condition was found and corrected, go to step 4 . If the condition was not found, go to step
3 .

3. Inspect the brake assist system for proper operation. See under TROUBLESHOOTING. If the condition

was found and corrected, go to step 4 . If the condition was not found, go to DIAGNOSTIC STARTING
POINTS under TROUBLE SHOOTING.

4. Road test the vehicle in order to confirm proper operation. See BRAKE SYSTEM VEHICLE ROAD

TEST under TESTING. If the condition is still present, go to step 2 . If the condition is not present,
system is okay.

PARK BRAKE WILL NOT HOLD OR RELEASE

1. If you were sent here from the Park Brake Symptom Test, go to step 2 . If you were not sent here from the

Park Brake Symptom Test, go to DIAGNOSTIC STARTING POINTS under TROUBLE SHOOTING.

2. Inspect the park brake system for proper operation. See PARK BRAKE SYSTEM DIAGNOSIS under

TROUBLE SHOOTING. If the condition was found and corrected, go to step 5 . If the condition was not
found and corrected, go to step 3 .

3. Inspect the disc brake system for proper operation. See DISC BRAKE SYSTEM DIAGNOSIS under

TROUBLE SHOOTING. If the condition was found and corrected, go to step 5 . If the condition was not
found and corrected, go to step 4 .

4. Inspect the hydraulic brake system for proper operation. See HYDRAULIC BRAKE SYSTEM

DIAGNOSIS under TROUBLE SHOOTING. If the condition was found and corrected, go to next step. 5
If the condition was not found and corrected, go to DIAGNOSTIC STARTING POINTS under
TROUBLESHOOTING.

5. Road test the vehicle in order to confirm proper operation. See BRAKE SYSTEM VEHICLE ROAD

TEST under SYSTEM TESTS. If the condition is still present, go to step 2 . If the condition is not
present, system is okay.

SYSTEM TESTS

BRAKE SYSTEM VEHICLE ROAD TEST

Preliminary Inspections

2004 Hummer H2

2003-04 BRAKES Disc - Hummer

1. Visually inspect easily accessible brake system components for obvious damage and/or leaks which may

indicate that the vehicle should not be driven until further inspections have been completed.

2. Inspect the brake master cylinder reservoir fluid level and adjust only if necessary for brake system road

testing. See MASTER CYLINDER RESERVOIR FILLING under BLEEDING BRAKE SYSTEM.

3. Inspect the tire inflation pressures and adjust as necessary.

4. Inspect the tire tread patterns to ensure that they are the same or very similar, especially per axle.

5. Ensure that the vehicle is not loaded unevenly prior to brake system road testing.

Road Testing Procedure

1. Start the engine and allow it to idle.

2. Check to see if the brake system warning light remains illuminated.

3. If the brake system warning light remains illuminated, DO NOT proceed to test drive the vehicle until it

is diagnosed and repaired. See GENERAL DIAGNOSIS under TROUBLESHOOTING.

4. Select a smooth, dry, clean and level road or large lot that is as free of traffic and obstacles as possible for

brake system low speed road testing.

5. With the transmission in PARK, lightly apply the brake pedal. Observe both the pedal feel and the pedal

travel.

6. If the brake pedal apply felt spongy, or the pedal travel was excessive. DO NOT drive the vehicle until it

is repaired.

7. If the brake pedal apply did not feel spongy and the pedal travel was not excessive, proceed to next step.

8. Release and apply the brakes.

9. While continuing to apply the brakes, shift the transmission into DRIVE, release the brakes and allow the

engine to idle the vehicle away from the stopped position. Observe for a slow release of the brake system.

10. With the aid of an assistant to observe the vehicle's performance from outside of the vehicle, drive the

vehicle at a low speed and lightly apply the brakes while driving past the assistant. Have the assistant
observe for brake system noise from the side of the vehicle closest to them, while you observe both the
pedal effort and the pedal travel.

11. If the brake pedal apply effort was excessive, or the pedal travel was excessive. DO NOT continue to test

drive the vehicle until it is repaired.

12. If the brake pedal apply effort was not excessive and the pedal travel was not excessive, proceed to next

step.

13. Drive the vehicle in the opposite direction, at the same low speed and lightly apply the brakes while

driving past the assistant. Have the assistant observe for brake system noise from the side of the vehicle
closest to him.

14. Drive the vehicle at a low speed and shift the transmission into NEUTRAL without applying the brakes.

Observe for a rapid deceleration in vehicle speed, indicating possible brake drag.

WARNING:

Road test a vehicle under safe conditions and while obeying all traffic
laws. DO NOT attempt any maneuvers that could jeopardize vehicle
control. Failure to adhere to these precautions could lead to serious
personal injury and vehicle damage.

2004 Hummer H2

2003-04 BRAKES Disc - Hummer