Chevrolet Silverado / GMC Sierra. Service manual — part 2373

9

Brake Pedal Travel Measurement and
Inspection.
Is the brake pedal travel distance within the
acceptable limits?

Go to Step 11

Go to Step 10

10

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 bushings 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.

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

Go to Step 12

Inspect for
internal and
external fluid
leaks and air in
the hydraulic
brake system
Go to Hydraulic
Brake System
Diagnosis

11

1. Check the power steering system fluid

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

-

2008 Chevrolet Silverado 1500

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

Leak Inspection.

Did you complete the inspections and any
necessary adjustments or replacements?

Go to Step 12

12

Perform the hydraulic booster functional test:

1. With the ignition OFF, depress the brake

pedal several times to deplete the power
reserve.

2. Depress and maintain 178 N (40 lb) of

force on the brake pedal.

3. Start the engine and observe pedal

operation.

Did the brake pedal fall slightly after the
engine was started, then hold?

IMPORTANT:

The brake pedal should fall slightly, then hold.

Go to Step 16

Go to Step 13

13

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 14

Go to Step 19

14

Perform the hydraulic booster functional test:

1. With the ignition OFF, depress the brake

pedal several times to deplete the power
reserve.

2. Depress and maintain 178 N (40 lb) of

force on the brake pedal.

3. Start the engine and observe pedal

operation.

IMPORTANT:

The brake pedal should fall slightly, then hold.

2008 Chevrolet Silverado 1500

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

Did the brake pedal fall slightly after the
engine was started, then hold?

Go to Step 16

Go to Step 19

15

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 14

Go to Step 19

16

Perform the short-term or accumulator reserve
leak-down test:

1. Start the engine and allow it to idle.

2. Charge the accumulator:

Turn the steering wheel to full-lock
position for 2 seconds ONLY and return
to rest.

3. Turn the ignition OFF.

4. Wait 90 seconds.

5. Depress the brake pedal 2 times to check

power reserve. Observe pedal effort.

Were both pedal applies power assisted?

IMPORTANT:

Both pedal applies should be assisted

The amount of assist could diminish
slightly with the second apply

If 2 power assisted pedal applications
could not be performed, the
accumulator is losing its gas charge

Go to Step 17

Go to Step 18

Perform the long-term reserve leak-down test:

1. Start the engine and allow it to idle.

2. Charge the accumulator:

Turn the steering wheel to full-lock
position for 2 seconds ONLY and return

2008 Chevrolet Silverado 1500

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

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.

17

to rest.

3. Turn the ignition OFF.

4. Wait 1 hour.

5. Depress the brake pedal 2 times to check

power reserve. Observe pedal effort.

Were both pedal applies power assisted?

IMPORTANT:

Both pedal applies should be assisted

The amount of assist could diminish
slightly with the second apply

If 2 power assisted pedal applications
could not be performed, the hydraulic
booster assembly is not retaining
power reserve

Go to Step 20

Go to Step 19

18

Replace the hydraulic brake booster
accumulator assembly, if applicable.
Did you complete the replacement?

Go to Step 20

-

19

Replace the hydraulic brake booster assembly.
Refer to Power Brake Booster Replacement
(Adjustable Pedals) or Power Brake
Booster Replacement (Non-Adjustable
Pedals).
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

-

2008 Chevrolet Silverado 1500

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