Chevrolet Silverado / GMC Sierra. Service manual — part 2372

14

Repair or replace any brake caliper that was not
operating properly. Refer to the appropriate
procedure:

Front Brake Caliper Overhaul (JH6,
JH7) or Front Brake Caliper
Replacement (JH6, JH7) or Front Brake
Caliper Replacement (JD9, JF3, JF7)

Rear Brake Caliper Overhaul (JH6,
JH7) or Rear Brake Caliper
Replacement (JH6, JH7) or Rear Brake
Caliper Replacement (JD9)

Did you complete the repair and/or replacement? Go to Step 21

-

15

Bleed the hydraulic brake system to observe for
the presence of air in the system and to observe
for an unrestricted and even flow of brake fluid
per axle during the bleeding procedure. Refer to
Hydraulic Brake System Bleeding (Pressure)
or Hydraulic Brake System Bleeding
(Manual).
Was there air in the system?

Go to Step 19

Go to Step 16

16

Was the flow of brake fluid unrestricted and even
per axle during the bleeding procedure?

Go to Step 21

Go to Step 17

1. Inspect the hydraulic brake pipes and

flexible brake hoses for signs of a fluid
restriction; such as being bent, kinked,
pinched or damaged. Refer to Brake Pipe
and Hose Inspection.

2. Replace any of the hydraulic brake pipes

and/or flexible brake hoses found to be
bent, kinked, pinched, or damaged. Refer to
the following procedures as necessary:

Front Brake Hose Replacement
(JD9, JF3, JF7)Front Brake Hose
Replacement (JH6, JH7)

Rear Brake Hose Replacement

2008 Chevrolet Silverado 1500

2008 BRAKES Hydraulic Brakes - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

17

(Frame to Axle - JH6, JH7)Rear
Brake Hose Replacement (Frame
to Axle - JD9, JF3 w/JL4)Rear
Brake Hose Replacement (Caliper -
JH6, JH7)Rear Brake Hose
Replacement (Caliper - JD9)Rear
Brake Hose Replacement (Frame
to Axle - JF3 w/o JL4, JF7)

Brake Pipe Replacement

3. If none of the hydraulic brake pipes or

flexible brake hoses were visibly bent,
kinked, pinched, or damaged, replace the
hydraulic brake flex hose at the restricted
location.

Did you find and correct a condition?

Go to Step 21

Go to Step 18

18

Replace the brake pressure modulator valve
(BPMV), in order to correct the hydraulic brake
dynamic rear proportioning mechanical
operation. Refer to Brake Pressure Modulator
Valve Replacement (JD9, JF3, JF7) or Brake
Pressure Modulator Valve Replacement
(JH6, JH7) .
Did you complete the replacement?

Go to Step 21

-

19

1. Inspect the hydraulic brake system

components for brake fluid seepage at a seal
and/or fitting location, which may have
drawn air into the system.

2. Inspect the hydraulic brake system

components for evidence of a recent repair,
which may have introduced air into the
system.

3. Repair or replace any of the components

found to be installed incorrectly or seeping
brake fluid.

Did you find and correct a condition?

Go to Step 21

Go to Step 20

1. Inspect the brake master cylinder for

2008 Chevrolet Silverado 1500

2008 BRAKES Hydraulic Brakes - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

BRAKE ASSIST SYSTEM DIAGNOSIS (HYDRAULIC ASSIST)

20

internal fluid leaks. Refer to Brake System
Internal Leak Test.

2. Repair or replace the brake master cylinder

if it is found to be leaking brake fluid
internally. Refer to Master Cylinder
Replacement (JD9, JF3, JF7) or Master
Cylinder Replacement (JH6, JH7).

Did you find and correct a condition?

Go to Step 21

Return to

Symptom Table

21

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

Hydraulic Brake

System OK

Return to

Symptom Table

-

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 system self-
applying when the steering wheel is being
turned?

Go to Step 11

Go to Step 9

4

Check the hydraulic assist system operation for
the presence of abnormal noise. Refer to
Hydraulic Brake Assist System Noise
Inspection.
Did the system operate normally from a noise
standpoint?

Go to Step 20

Go to Step 5

1. Check the power steering system fluid

level and adjust the level if necessary.
Refer to Checking and Adding Power

2008 Chevrolet Silverado 1500

2008 BRAKES Hydraulic Brakes - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

5

Steering Fluid (With Hydroboost) or
Checking and Adding Power Steering
Fluid (Without Hydroboost) .

2. Inspect the power steering pump drive

belt for proper tension and excessive
wear.

3. Inspect the power steering pressure and

return hoses for proper routing, possible
ground-outs, possible restrictions, and/or
damage.

4. Inspect the hydraulic brake booster for

leaks. Refer to Power Brake Booster
Leak Inspection.

Did you find and correct a condition?

Go to Step 20

Go to Step 6

6

1. Position the vehicle on the ground with

wheels straight ahead.

2. Start the engine and allow it to idle.

3. Apply the brake pedal with moderate

force 130-200 N (30-45 lb). Observe for
noises.

4. Release the brakes and turn the steering

wheel slightly from side to side. Observe
for noises.

5. Compare the noise levels between brake

apply and steering input.

Was the abnormal noise heard ONLY during
brake apply?

Go to Step 12

Go to Step 7

7

Perform the Power Steering System Test
procedure to determine if there are any
restrictions in the system. Refer to Power
Steering System Test .
Did you find and correct a condition?

Go to Step 20

Go to Step 8

8

During the noise inspection, did the hydraulic
brake booster produce abnormal noises?

Go to Step 12

Go to Step 20

Inspect for proper brake pedal travel. Refer to

2008 Chevrolet Silverado 1500

2008 BRAKES Hydraulic Brakes - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado