Hummer H3. Manual — part 1314

BRAKE FLUID LOSS

Brake Fluid Loss

Did you find and correct a condition?

Go to Step 5 Brakes

5

1. Install or connect components that

were removed or disconnected during
diagnosis.

2. Road test the vehicle in order to

confirm proper operation. Refer to
Brake System Vehicle Road Test.

Is the condition still present?

Go to Step 2

System OK

Step

Action

Yes

No

DEFINITION: Brake fluid level is low not related to lining wear.

1

Were you sent here from the Hydraulic
Brake Symptom table?

Go to Step 2

Go to
Diagnostic
Starting Point -
Hydraulic
Brakes

2

1. Inspect the following hydraulic brake

system components for brake fluid
leaks:

Flexible brake hose connections;
threaded and bolted

Flexible brake hose crimp joints

Brake pipe fittings

Caliper piston seals

Wheel cylinder piston seals, if
equipped

Master cylinder reservoir

Master cylinder reservoir low
pressure hose, if equipped

Brake pressure modulator valve
(BPMV) assembly, if equipped

2. Repair or replace components as

2007 Hummer H3

2007 BRAKES Hydraulic Brakes - H3

necessary. Refer to Hydraulic Brake
System Diagnosis.

Did you find and correct a condition?

Go to Step 8

Go to Step 3

3

Is the vehicle equipped with a vacuum brake
booster?

Go to Step 4

Go to Step 6

4

1. Disconnect the vacuum check valve

from the booster to relieve vacuum
reserve.

2. Separate the master cylinder from the

vacuum brake booster. Do not
disconnect any brake pipes.

3. Inspect the rear of the master cylinder

for a brake fluid leak.

4. Inspect for brake fluid in the vacuum

brake booster.

Did you find a brake fluid leak?

Go to Step 5

Go to
Diagnostic
Starting Point -
Hydraulic
Brakes

5

Replace the brake master cylinder and the
vacuum brake booster.
Did you complete the replacement?

Go to Step 8

-

6

1. Wipe clean the external surface of the

master cylinder to hydraulic brake
booster area, if equipped.

2. Separate the master cylinder from the

hydraulic brake booster, if equipped.
Do not disconnect any brake pipes.

3. Inspect the rear of the master cylinder

for a brake fluid leak.

Did you find a brake fluid leak?

Go to Step 7

Go to
Diagnostic
Starting Point -
Hydraulic
Brakes

7

Replace the brake master cylinder.
Did you complete the replacement?

Go to Step 8

-

8

1. Install or connect components that

were removed or disconnected during
diagnosis.

2. Road test the vehicle to confirm proper

2007 Hummer H3

2007 BRAKES Hydraulic Brakes - H3

DISC BRAKE SYSTEM DIAGNOSIS

Test Description

The numbers below refer to the step numbers on the diagnostic table.

9: Lubricant leaks from non-brake system components may come in contact with and
contaminate brake system components.

10: Lubricant leaks from non-brake system components may come in contact with and
contaminate brake system components.

12: Disc brake rotor shields/backing plates that come in contact with disc brake rotors may
cause brake system noise.

15: Disc brake rotor thickness variation that exceeds the maximum acceptable level can
cause brake pulsation.

19: Disc brake rotor thickness variation that exceeds the maximum acceptable level can
cause brake pulsation.

22: Disc brake rotor assembled lateral runout (LRO) that exceeds the maximum acceptable
level can lead to thickness variation.

Disc Brake System Diagnosis

operation. Refer to Brake System
Vehicle Road Test.

Is the condition still present?

Go to Step 2

System OK

Step

Action

Yes

No

DEFINITION: This diagnostic table is designed to diagnose ONLY the components of the
DISC brake system in order to determine if the DISC brake 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

Visually inspect the disc brake pads for the
following conditions:
Refer to Brake Pad Inspection .

2007 Hummer H3

2007 BRAKES Hydraulic Brakes - H3

2

Lining thickness below specifications

Uneven and/or abnormal wear, edge-
to-edge and/or side-to-side

Looseness or damage, including pad
hardware

Evidence of contamination from an
external substance

Did you find any conditions to indicate a
concern with any of the front and/or rear
disc brake pads?

Go to Step 3

Go to Step 12

3

Are any of the front and/or rear disc brake
pads contaminated?

Go to Step 8

Go to Step 4

4

Are any of the front and/or rear disc brake
pads worn unevenly?

Go to Step 7

Go to Step 5

5

Are any of the front and/or rear disc brake
pads and/or pad hardware loose or
damaged?

Go to Step 7

Go to Step 6

6

1. Remove and inspect the worn disc

brake pads for glazing, looseness, heat
spots or damage.

2. Replace the worn disc brake pads as a

complete axle set. Refer to Front
Disc Brake Pads Replacement
and/or Rear Disc Brake Pads
Replacement .

Did you complete the inspection and
replacement?

Go to Step 12

-

NOTE:

Support the brake caliper with heavy
mechanic wire or equivalent, whenever it
is separated from its mount and the
hydraulic flexible brake hose is still
connected. Failure to support the caliper
in this manner will cause the flexible
brake hose to bear the weight of the
caliper, which may cause damage to the

2007 Hummer H3

2007 BRAKES Hydraulic Brakes - H3