Hummer H3. Manual — part 1317

HYDRAULIC BRAKE SYSTEM DIAGNOSIS

Hydraulic Brake System Diagnosis

Did you complete the operation?

Return to
Symptom Table

Step

Action

Yes

No

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

2

Inspect and adjust the brake fluid level in
the brake master cylinder. Refer to Master
Cylinder Reservoir Filling.
Was the brake fluid level low?

Go to Step 3

Go to Step 4

3

1. Inspect the brake fluid for the

following conditions, indicating brake
fluid contamination:

Fluid separation, indicating 2
types of fluid are present

Swirled appearance - oil-
based substance

Layered appearance -
silicone-based substance

Fluid discoloration

Cloudy appearance -
moisture

Dark appearance/suspended
particles in fluid - dirt, rust,
corrosion, brake dust

2. Inspect the master cylinder reservoir

cap diaphragm and the reservoir-to-

2007 Hummer H3

2007 BRAKES Hydraulic Brakes - H3

master cylinder grommets for swelling,
indicating fluid contamination.

Do any of the above conditions exist?

Go to Step 5

Go to Step 6

4

1. Inspect the brake fluid for the

following conditions, indicating brake
fluid contamination:

Fluid separation, indicating 2
types of fluid are present

Swirled appearance - oil-
based substance

Layered appearance -
silicone-based substance

Fluid discoloration

Cloudy appearance -
moisture

Dark appearance/suspended
particles in fluid - dirt, rust,
corrosion, brake dust

2. Inspect the master cylinder reservoir

cap diaphragm and the reservoir-to-
master cylinder grommets for swelling,
indicating fluid contamination.

Do any of the above conditions exist?

Go to Step 5

Go to Step 12

1. Flush the hydraulic brake system.

Refer to Hydraulic Brake System
Flushing.

2. If the brake fluid WAS contaminated

with an oil-based or a silicone-based
fluid, indicated by fluid separation
and/or a swollen master cylinder
reservoir cap diaphragm and/or
swollen reservoir-to-master cylinder
grommets, perform the following steps.
Refer to the procedures indicated.

1. Remove ALL of the following

2007 Hummer H3

2007 BRAKES Hydraulic Brakes - H3

5

components listed. Each
component contains internal
rubber seals/linings which have
been contaminated.

2. Clean out the hydraulic brake

pipes using denatured alcohol or
equivalent.

3. Dry the brake pipes using non-

lubricated, filtered air.

4. Repair or replace ALL of the

following components listed.
Each component contains internal
rubber seals/linings which have
been contaminated.

Front Brake Hose
Replacement

Rear Brake Hose
Replacement

Front Brake Caliper
Overhaul or Front Brake
Caliper Replacement

Rear Brake Caliper
Overhaul or Rear Brake
Caliper Replacement

Brake Master Cylinder
with Power Brake
Booster and Chassis
Control Module
Replacement (LHD)
Brake Master Cylinder
with Power Brake
Booster and Chassis
Control Module
Replacement (RHD)

3. If the brake fluid was NOT

contaminated with an oil-based fluid,
but WAS contaminated with water or

-

2007 Hummer H3

2007 BRAKES Hydraulic Brakes - H3

dirt, rust, corrosion, and/or brake dust,
replace the brake master cylinder
reservoir cap diaphragm which may
have allowed moisture or dirt to enter
the system.

4. Refill and bleed the hydraulic brake

system. Refer to Hydraulic Brake
System Bleeding (Manual) or
Hydraulic Brake System Bleeding
(Pressure).

Did you complete the operation and any
required repairs and/or replacements?

Go to Step 9

1. Inspect the following hydraulic brake

system components for external fluid
leaks. Repair or replace any of the
components found to be leaking brake
fluid. Refer to the appropriate
procedures:

Master Cylinder Replacement

Brake master cylinder reservoir
cap assembly

Master Cylinder Reservoir
Replacement

Power Brake Booster Inlet
Hose Replacement

Power Brake Booster Outlet
Front Pipe Replacement

Power Brake Booster
Replacement

Hydraulic Brake Booster
Accumulator Replacement

Front Brake Hose
Replacement

Rear Brake Hose Replacement

2007 Hummer H3

2007 BRAKES Hydraulic Brakes - H3