Hummer H3. Manual — part 1319

BRAKE ASSIST SYSTEM DIAGNOSIS

Brake Assist System Diagnosis

Step

Action

Yes

No

DEFINITION: This diagnostic table is designed to diagnose ONLY the components of the
brake ASSIST system in order to determine if the brake ASSIST system is operating
properly. You will be directed by the appropriate Symptom Table to go to other brake
system diagnostic tables as appropriate.

1

Were you sent here from a Brake Symptom
Table?

Go to Step 2

Go to
Diagnostic
Starting Point -
Hydraulic
Brakes

2

Is the symptom related to brake system
noise?

Go to Step 4

Go to Step 3

3

Is the symptom related to the brake pedal
travel feel?

Go to Step 12

Return to
Symptom Table

4

Check the hydraulic assist system operation
for the presence of abnormal noise. Refer to
Hydraulic Brake Assist System Noise
Inspection.
Did the noise inspection indicate a concern
with the power brake booster pump
dampers?

Go to Step 5

Go to Step 6

5

Replace the power brake booster pump
dampers. Refer to Power Brake Booster
Replacement.
Did you complete the replacement?

Go to Step 6

-

6

Did the noise inspection indicate a possible
restriction in the power brake booster inlet
hose?

Go to Step 7

Go to Step 8

7

Replace the restricted power brake booster
inlet hose. Refer to Power Brake Booster
Inlet Hose Replacement.
Did you complete the replacement?

Go to Step 8

-

8

Did the noise inspection indicate a possible
restriction in the power brake booster outlet
pipe?

Go to Step 9

Go to Step 10

2007 Hummer H3

2007 BRAKES Hydraulic Brakes - H3

9

Replace the restricted power brake booster
outlet pipe. Refer to Power Brake Booster
Outlet Front Pipe Replacement.
Did you complete the replacement?

Go to Step 10

-

10

During the inspection, did the hydraulic
brake booster pump and motor make
abnormal noises?

Go to Step 11

Go to Step 9

11

Replace the hydraulic brake booster
assembly. Refer to Power Brake Booster
Replacement.
Did you complete the replacement?

Go to Step 20

-

12

Inspect for proper brake pedal travel. Refer
to Brake Pedal Travel Measurement
and Inspection.
Is the brake pedal travel distance within the
acceptable limits?

Go to Step 12

Go to Step 13

13

1. Inspect for worn, missing, misaligned,

bent or damaged brake pedal system
components.

For the brake pedal pushrod
component inspection, refer to
Brake Pedal Pushrod
Inspection .

Inspect the brake pedal clevis for
excessive wear and/or damage
and inspect the brake pedal for a
misaligned, bent, and/or
damaged condition.

2. Replace the brake pedal system

components that are worn, missing,
misaligned, bent or damaged. Refer to
the following procedures as necessary.

Brake Pedal Assembly
Replacement (LHD)Brake
Pedal Assembly Replacement
(RHD)

Master Cylinder Replacement

2007 Hummer H3

2007 BRAKES Hydraulic Brakes - H3

for a bent or damaged pedal
pushrod replacement

Did you find and replace any worn, missing,
misaligned, bent or damaged brake pedal
system components?

Go to Step 14

Go to Step 15

14

Reinspect for proper brake pedal travel.
Refer to Brake Pedal Travel
Measurement and Inspection.
Is the brake pedal travel distance within the
acceptable limits?

Go to Step 16

Go to Step 15

15

Check for air trapped in the hydraulic
booster pump and motor assembly. Refer to
Hydraulic Brake System Bleeding
(Manual) or Hydraulic Brake System
Bleeding (Pressure).
Did you complete the hydraulic brake
system bleeding procedure?

Go to Step 16

-

16

1. With the ignition OFF, depress the

brake pedal 20 times or until the
brake pedal stroke increases.

2. Maintain moderate foot pressure on

the brake pedal and start the engine.
Observe pedal operation.

Did the brake pedal push back, then hold
after the engine was started?

Go to Step 17

Go to Step 19

17

1. Release the brake pedal.

2. Start the engine to pressurize the

system.

3. Turn the ignition OFF.

4. Wait 1 hour, then depress the brake

pedal 4 times to check for hydraulic
brake booster accumulator reserve
leak-down. Observe pedal effort.

Did the brake pedal apply effort
significantly increase when the brake pedal

2007 Hummer H3

2007 BRAKES Hydraulic Brakes - H3

BRAKE SYSTEM VEHICLE ROAD TEST

Preliminary Inspections

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. Refer to Master Cylinder Reservoir Filling.

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 lamp remains illuminated.

was applied the fourth time?

Go to Step 18

Go to Step 20

18

Replace the hydraulic brake booster
accumulator assembly. Refer to Hydraulic
Brake Booster Accumulator
Replacement.
Did you complete the replacement?

Go to Step 20

-

19

Replace the pump and motor assembly.
Refer to Power Brake Booster
Replacement.
Did you complete the replacement?

Go to Step 20

-

20

Install or connect any components that were
removed or disconnected during diagnosis.
Did you complete the operation?

Brake Assist
System OK
Return to
Symptom Table

-

CAUTION: 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.

2007 Hummer H3

2007 BRAKES Hydraulic Brakes - H3