Chevrolet Silverado / GMC Sierra. Service manual — part 2388

21. After completing the final wheel hydraulic circuit bleeding procedure, ensure that each of

the 4 wheel hydraulic circuit bleeder valves are properly tightened.

22. Close the J 29532 , or equivalent, fluid tank valve, then disconnect the J 29532 , or

equivalent, from the J 35589-A . See Special Tools.

23. Remove the J 35589-A from the brake master cylinder reservoir. See Special Tools.

24. Fill the brake master cylinder reservoir to the maximum-fill level with Delco Supreme 11®,

GM P/N 12377967 (Canadian P/N 992667), or equivalent DOT-3 brake fluid from a clean,
sealed brake fluid container.

25. Slowly depress and release the brake pedal. Observe the feel of the brake pedal.

26. If the brake pedal feels spongy perform the following steps:

1. Inspect the brake system for external leaks. Refer to Brake System External Leak

Inspection .

2. Using a scan tool, perform the antilock brake system automated bleeding procedure to

remove any air that may have been trapped in the brake pressure modulator valve
(BPMV). Refer to Antilock Brake System Automated Bleed Procedure (With
JL4) Antilock Brake System Automated Bleed Procedure (Without JL4) .

27. Turn the ignition key ON, with the engine OFF. Check to see if the brake system warning

lamp remains illuminated.

28. If the brake system warning lamp remains illuminated, refer to Symptoms - Hydraulic

Brakes.

HYDRAULIC BRAKE SYSTEM BLEEDING (MANUAL)

IMPORTANT: If the brake system warning lamp remains illuminated, DO

NOT allow the vehicle to be driven until it is diagnosed and
repaired.

CAUTION: Refer to Brake Fluid Irritant Caution .

NOTE:

Refer to Brake Fluid Effects on Paint and Electrical Components
Notice .

NOTE:

When adding fluid to the brake master cylinder reservoir, use only
Delco Supreme 11®, GM P/N 12377967 (Canadian P/N 992667), or
equivalent DOT-3 brake fluid from a clean, sealed brake fluid

2008 Chevrolet Silverado 1500

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

1. Place a clean shop cloth beneath the brake master cylinder to prevent brake fluid spills.

2. With the ignition OFF and the brakes cool, apply the brakes 3-5 times, or until the brake

pedal effort increases significantly, in order to deplete the brake booster power reserve.

3. If you have performed a brake master cylinder bench bleeding on this vehicle, or if you

disconnected the brake pipes from the master cylinder, you must perform the following
steps:

1. Ensure that the brake master cylinder reservoir is full to the maximum-fill level. If

necessary add Delco Supreme 11®, GM P/N 12377967 (Canadian P/N 992667), or
equivalent DOT-3 brake fluid from a clean, sealed brake fluid container.

If removal of the reservoir cap and diaphragm is necessary, clean the outside of the
reservoir on and around the cap prior to removal.

2. With the rear brake pipe installed securely to the master cylinder, loosen and separate

the front brake pipe from the front port of the brake master cylinder.

3. Allow a small amount of brake fluid to gravity bleed from the open port of the master

cylinder.

4. Reconnect the brake pipe to the master cylinder port and tighten securely.

5. Have an assistant slowly depress the brake pedal fully and maintain steady pressure on

the pedal.

6. Loosen the same brake pipe to purge air from the open port of the master cylinder.

7. Tighten the brake pipe, then have the assistant slowly release the brake pedal.

8. Wait 15 seconds, then repeat steps 3.3-3.7 until all air is purged from the same port of

the master cylinder.

9. With the front brake pipe installed securely to the master cylinder, after all air has

been purged from the front port of the master cylinder, loosen and separate the rear
brake pipe from the master cylinder, then repeat steps 3.3-3.8.

10. After completing the final master cylinder port bleeding procedure, ensure that both of

the brake pipe-to-master cylinder fittings are properly tightened.

4. Fill the brake master cylinder reservoir with Delco Supreme 11®, GM P/N 12377967

(Canadian P/N 992667), or equivalent DOT-3 brake fluid from a clean, sealed brake fluid
container. Ensure that the brake master cylinder reservoir remains at least half-full during

container. The use of any type of fluid other than the recommended
type of brake fluid, may cause contamination which could result in
damage to the internal rubber seals and/or rubber linings of
hydraulic brake system components.

2008 Chevrolet Silverado 1500

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

this bleeding procedure. Add fluid as needed to maintain the proper level.

Clean the outside of the reservoir on and around the reservoir cap prior to removing the cap
and diaphragm.

5. Install a proper box-end wrench onto the RIGHT REAR wheel hydraulic circuit bleeder

valve.

6. Install a transparent hose over the end of the bleeder valve.

7. Submerge the open end of the transparent hose into a transparent container partially filled

with Delco Supreme 11®, GM P/N 12377967 (Canadian P/N 992667), or equivalent DOT-
3 brake fluid from a clean, sealed brake fluid container.

8. Have an assistant slowly depress the brake pedal fully and maintain steady pressure on the

pedal.

9. Loosen the bleeder valve to purge air from the wheel hydraulic circuit.

10. Tighten the bleeder valve, then have the assistant slowly release the brake pedal.

11. Wait 15 seconds, then repeat steps 8-10 until all air is purged from the same wheel hydraulic

circuit.

12. With the right rear wheel hydraulic circuit bleeder valve tightened securely, after all air has

been purged from the right rear hydraulic circuit install a proper box-end wrench onto the
LEFT REAR wheel hydraulic circuit bleeder valve.

13. Install a transparent hose over the end of the bleeder valve, then repeat steps 7-11.

14. With the left rear wheel hydraulic circuit bleeder valve tightened securely, after all air

purged from the left rear hydraulic circuit, install a proper box-end wrench onto the RIGHT
FRONT wheel hydraulic circuit bleeder valve.

15. Install a transparent hose over the end of the bleeder valve, then repeat steps 7-11.

16. With the right front wheel hydraulic circuit bleeder valve tightened securely, after all air has

been purged from the right front hydraulic circuit, install a proper box-end wrench onto the
LEFT FRONT wheel hydraulic circuit bleeder valve.

17. Install a transparent hose over the end of the bleeder valve, then repeat steps 7-11.

18. After completing the final wheel hydraulic circuit bleeding procedure, ensure that each of

the 4 wheel hydraulic circuit bleeder valves are properly tightened.

19. Fill the brake master cylinder reservoir to the maximum-fill level with Delco Supreme 11®,

GM P/N 12377967 (Canadian P/N 992667), or equivalent DOT-3 brake fluid from a clean,
sealed brake fluid container.

20. Slowly depress and release the brake pedal. Observe the feel of the brake pedal.

21. If the brake pedal feels spongy, repeat the bleeding procedure again. If the brake pedal still

2008 Chevrolet Silverado 1500

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

feels spongy after repeating the bleeding procedure, perform the following steps:

1. Inspect the brake system for external leaks. Refer to Brake System External Leak

Inspection .

2. Pressure bleed the hydraulic brake system in order to purge any air that may still be

trapped in the system.

22. Turn the ignition key ON, with the engine OFF. Check to see if the brake system warning

lamp remains illuminated.

23. If the brake system warning lamp remains illuminated, refer to Symptoms - Hydraulic

Brakes.

HYDRAULIC BRAKE SYSTEM FLUSHING

1. Inspect the brake fluid for the following conditions, indicating brake fluid contamination:

Fluid separation, indicating two types of fluid are present; a substance other than the
recommended brake fluid has been introduced into the brake hydraulic system

Swirled appearance - oil-based substance

Layered appearance - silicone-based substance

Fluid discoloration, indicating the presence of moisture or particles that have been
introduced into the brake hydraulic system

IMPORTANT: If the brake system warning lamp remains illuminated, DO

NOT allow the vehicle to be driven until it is diagnosed and
repaired.

CAUTION: Refer to Brake Fluid Irritant Caution .

NOTE:

Refer to Brake Fluid Effects on Paint and Electrical Components
Notice .

NOTE:

When adding fluid to the brake master cylinder reservoir, use only
Delco Supreme 11®, GM P/N 12377967 (Canadian P/N 992667), or
equivalent DOT-3 brake fluid from a clean, sealed brake fluid
container. The use of any type of fluid other than the recommended
type of brake fluid, may cause contamination which could result in
damage to the internal rubber seals and/or rubber linings of
hydraulic brake system components.

2008 Chevrolet Silverado 1500

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