Hummer H3. Manual — part 1320

3. If the brake system warning lamp remains illuminated, DO NOT proceed to test drive the

vehicle until it is diagnosed and repaired. Refer to Symptoms - Hydraulic Brakes.

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 step 8.

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 step 13.

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.

15. Select a smooth, dry, clean and level road that is as free of heavy traffic as possible for

brake system moderate speed road testing.

16. Drive the vehicle at a moderate speed. Observe for a pull and/or incorrect tracking of the

vehicle without the brakes applied.

17. While continuing to drive the vehicle at a moderate speed, perform several light applies of

the brakes. Observe the pedal effort and the pedal travel, observe for brake system noise,
pulsation and/or brake drag.

18. If the brake pedal apply effort was excessive or the pedal travel was excessive, DO NOT

2007 Hummer H3

2007 BRAKES Hydraulic Brakes - H3

continue to test drive the vehicle until it is repaired.

19. If the brake pedal apply effort was not excessive and the pedal travel was not excessive,

proceed to step 20.

20. While continuing to drive the vehicle at a moderate speed, perform several moderate applies

of the brakes. Observe the pedal effort and the pedal travel, observe for brake system
pulsation and/or uneven braking action - either side to side or front to rear.

A small amount of vehicle front end dip is expected during a moderate apply of the brakes.

21. 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.

BRAKE PEDAL TRAVEL MEASUREMENT AND INSPECTION

Tools Required

J 28662 Brake Pedal Effort Gage. See Special Tools.

Inspection Procedure

1. Install the J 28662 to the brake pedal. See Special Tools.

2. Release the park brake.

3. Place the engine switch in the ON position.

2007 Hummer H3

2007 BRAKES Hydraulic Brakes - H3

Fig. 6: Measuring Brake Pedal Travel
Courtesy of GENERAL MOTORS CORP.

4. Measure and record the distance (1) from the brake pedal to the rim of the steering wheel;

note the points of measurement.

5. Apply and maintain the brakes with 134 N (30 lb) of force to the brake pedal, as indicated

on the J 28662 . See Special Tools.

6. While maintaining 134 N (30 lb) of force to the brake pedal, measure and record the

distance (2) from the same point on the brake pedal to the same point on the rim of the
steering wheel.

7. Release the brakes and repeat steps 4 and 5 to obtain a second measurement. After obtaining

2007 Hummer H3

2007 BRAKES Hydraulic Brakes - H3

a second measurement, proceed to step 8.

8. Average the first and second measurements recorded during the two applies of the brakes.

9. Subtract the initial measurement, unapplied (1), from the averaged, applied measurement

(2) to obtain the brake pedal travel distance.

Specification: Maximum brake pedal travel (measured with the ignition ON and the brakes
cool): 61 mm (2.40 in)

HYDRAULIC BRAKE ASSIST SYSTEM NOISE INSPECTION

Tools Required

J 28662 Brake Pedal Effort Gage. See Special Tools.

Inspection Procedure

1. Install the J 28662 to the brake pedal. See Special Tools.

2. Start the engine and allow it to idle. Ensure that the wheels are directed straight ahead.

3. Apply and maintain the brakes with 111 N.m (25 lb) of force to the brake pedal, as

indicated on the J 28662 . See Special Tools. Observe for noises.

4. Quickly release the brakes. Observe for noises.

5. Check the pump and motor are running. If the noise is excessive/abnormal, check the

following:

Damaged high pressure pipe

Defective pump and motor mounts

Defective pump and motor assembly

6. Apply the brakes with 178 N.m (40 lb) of force to the brake pedal, as indicated on the J

28662 , then gradually increase pedal effort up to 445 N. See Special Tools.m (100 lb) of
force for not more than 5 seconds at a time. Observe for noises.

7. Quickly release the brakes. Observe for noises.

8. If a hiss noise was apparent and increased during the brake system increasing apply of 178-

445 N.m (40-100 lb) of force, the hydraulic brake booster assist system is operating
normally from an audible standpoint.

9. If a clunk, chatter, and/or clicking noise was apparent during the quick release of the brakes

IMPORTANT: Do NOT apply 445 N.m (100 lb) of force or more to the brake

system pedal for more than 5 seconds at a time.

2007 Hummer H3

2007 BRAKES Hydraulic Brakes - H3