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Chevrolet Silverado / GMC Sierra. Manual - part 2391
POWER BRAKE BOOSTER LEAK INSPECTION
3. Disconnect the brake master cylinder pressure sensor electrical connector.
1
Brake Master Cylinder Pressure Sensor
Procedure
1. After the installation is complete, bleed the hydraulic brake system at the
front wheels only. It is not necessary the bleed the rear hydraulic circuit.
Refer to Hydraulic Brake System Bleeding (Pressure) or Hydraulic
Brake System Bleeding (Manual).
2. Do not lubricate the sensor threads prior to installation.
Tighten: 26 N.m (19 lb ft)
NOTE:
Refer to Fastener Notice .
2
Brake Master Cylinder Pressure Sensor O-ring Seal
Procedure
1. Discard the O-ring seal.
2. Do not lubricate the O-ring seal prior to installation.
2008 Chevrolet Silverado 1500
2008 BRAKES Hydraulic Brakes - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
Fig. 37: View Of Power Brake Booster
Courtesy of GENERAL MOTORS CORP.
1. Check the power steering system fluid 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) .
IMPORTANT: The power brake booster may appear wet due to excessive
assembly fluid during manufacturing or brake fluid that could
have been spilled during system fill. In an effort to prevent
unnecessary replacement of the power steering boosters,
perform the following power brake booster leak inspection
before replacing the power brake booster.
2008 Chevrolet Silverado 1500
2008 BRAKES Hydraulic Brakes - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
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
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