Chevrolet Silverado / GMC Sierra. Manual — part 2391

2. Clean any fluid off all of the following areas:

The power brake booster housing and fittings 3

The joint between the power brake booster housing and master cylinder 2

The end cap

The joint between the power brake booster housing and end cap 1

3. Start the engine and allow the power steering fluid to reach operating temperature.

4. Allow the engine to idle and slowly apply the brake pedal to run-out, holding until the

power steering pump reaches the pressure relief valve setting and hisses. Then maintain this
brake pedal force for approximately two seconds longer, then release the brake pedal.

5. Allow the engine to idle with your foot off the brake for fifteen seconds.

6. Repeat steps 4 and 5 four more times.

7. With the engine idling, turn the steering wheel from stop to stop four times and hold the

wheel at each stop for two seconds.

8. Increase the engine idle speed to approximately 1000 RPM and turn the steering wheel from

stop to stop six times at a rate of one turn of the steering wheel approximately every second.
Do not hold the wheel at full stop.

9. Allow the engine to idle with your foot off the brake for thirty seconds.

10. With the engine idling, apply the brake pedal to run-out and hold the pedal force at run-out

for approximately one second and the release the brake pedal.

11. Repeat steps 7 through 10 four times.

12. Allow the engine to idle for thirty seconds and then turn the engine off.

IMPORTANT: To properly diagnose a leak condition, aid from an assistant

may be required. The power brake booster system must be
observed while completing this inspection.

IMPORTANT: Do not hold the wheel for more than three seconds at full

stop, as this will increase the fluid temperature in the pump
above operating temperature.

2008 Chevrolet Silverado 1500

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

Fig. 38: View Of Power Brake Booster
Courtesy of GENERAL MOTORS CORP.

13. Inspect the power brake booster for any leaks

IMPORTANT: On low mileage vehicles, at joint between the power brake

booster housing and end cap 1, light moisture is acceptable.
If fluid droplets develop, the power brake booster must be
replaced.

IMPORTANT: A leak between the power steering brake booster 2 and the

master cylinder is not acceptable. If a leak is present, the
type of fluid must be determined. Power steering fluid
indicates that the power brake booster needs to be replaced.

2008 Chevrolet Silverado 1500

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