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2. Inspect the brake master cylinder reservoir fluid level and adjust only if necessary for brake system road testing. Refer to Master Cylinder Reservoir Filling. 3. Inspect the tire inflation pressures and adjust as necessary. 4. Inspect the tire tread patterns to ensure that they are the same or very similar, especially per axle. 5. Ensure that the vehicle is not loaded unevenly prior to brake system road testing. Road Testing Procedure 1. Start the engine and allow it to idle. 2. Check to see if the brake system warning lamp remains illuminated. 3. If the brake system warning lamp remains illuminated, DO NOT proceed to test drive the vehicle until it is diagnosed and repaired. Refer to Symptoms - Hydraulic Brakes. 4. Select a smooth, dry, clean and level road or large lot that is as free of traffic and obstacles as possible for brake system low speed road testing. 5. With the transmission in PARK, lightly apply the brake pedal. Observe both the pedal feel and the pedal travel. 6. If the brake pedal apply felt spongy, or the pedal travel was excessive, DO NOT drive the vehicle until it is repaired. 7. If the brake pedal apply did not feel spongy and the pedal travel was not excessive, proceed to step 8. 8. Release and apply the brakes. 9. While continuing to apply the brakes, shift the transmission into DRIVE, release the brakes and allow the engine to idle the vehicle away from the stopped position. Observe for a slow 10. With the aid of an assistant to observe the vehicle's performance from outside of the vehicle, drive the vehicle at a low speed and lightly apply the brakes while driving past the assistant. 11. If the brake pedal apply effort was excessive, or the pedal travel was excessive, DO NOT continue to test drive the vehicle until it is repaired. CAUTION: Road test a vehicle under safe conditions and while obeying all traffic laws. Do not attempt any maneuvers that could
2008 Chevrolet Silverado 1500 2008 BRAKES Hydraulic Brakes - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
12. If the brake pedal apply effort was not excessive and the pedal travel was not excessive, proceed to step 13. 13. Drive the vehicle in the opposite direction, at the same low speed and lightly apply the brakes while driving past the assistant. Have the assistant observe for brake system noise 14. Drive the vehicle at a low speed and shift the transmission into NEUTRAL without applying the brakes. Observe for a rapid deceleration in vehicle speed, indicating possible brake 15. Select a smooth, dry, clean and level road that is as free of heavy traffic as possible for brake system moderate speed road testing. 16. Drive the vehicle at a moderate speed. Observe for a pull and/or incorrect tracking of the vehicle without the brakes applied. 17. While continuing to drive the vehicle at a moderate speed, perform several light applies of the brakes. Observe the pedal effort and the pedal travel, observe for brake system noise, 18. If the brake pedal apply effort was excessive, or the pedal travel was excessive, DO NOT continue to test drive the vehicle until it is repaired. 19. If the brake pedal apply effort was not excessive and the pedal travel was not excessive, proceed to step 20. 20. While continuing to drive the vehicle at a moderate speed, perform several moderate applies of the brakes. Observe the pedal effort and the pedal travel, observe for brake system A small amount of vehicle front end dip is expected during a moderate apply of the brakes. 21. If the brake pedal apply effort was excessive, or the pedal travel was excessive, DO NOT continue to test drive the vehicle until it is repaired. BRAKE PEDAL TRAVEL MEASUREMENT AND INSPECTION Tools Required J 28662 Brake Pedal Effort Gage. See Special Tools. Measurement and Inspection 1. With the ignition OFF and the brakes cool, apply the brakes 3-5 times, or until the brake pedal becomes firm, in order to deplete the brake booster power reserve. 2. Install the J 28662 to the brake pedal. See Special Tools.
2008 Chevrolet Silverado 1500 2008 BRAKES Hydraulic Brakes - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
Fig. 2: Measuring Brake Pedal Travel 3. Measure and record the distance (1) from the brake pedal to the rim of the steering wheel; note the points of measurement. 4. Apply and maintain the brakes with 445 N (100 lb) of force to the brake pedal, as indicated on the J 28662 . See Special Tools. 5. While maintaining 445 N (100 lb) of force to the brake pedal, measure and record the distance (2) from the same point on the brake pedal to the same point on the rim of the 6. Release the brakes and repeat steps 4 and 5 to obtain a second measurement. After obtaining
2008 Chevrolet Silverado 1500 2008 BRAKES Hydraulic Brakes - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
a second measurement, proceed to step 7. 7. Average the first and second measurements recorded during the two applies of the brakes. 8. Subtract the initial measurement, unapplied (1), from the averaged, applied measurement (2) to obtain the brake pedal travel distance. Specification: Vacuum assist equipped, maximum brake pedal travel (measured with the ignition Hydraulic assist equipped, maximum brake pedal travel (measured with the ignition BRAKE SYSTEM VACUUM SOURCE TEST 1. Disconnect the engine vacuum hose from the vacuum brake booster check valve. 2. Install a vacuum gage to the engine vacuum hose. 3. Start the engine and allow the engine to idle until normal operating temperatures are reached. 4. With the vehicle in PARK, the engine idling, and the air conditioning (A/C) system OFF, check to see if the engine vacuum reading is within the specified normal engine vacuum Specification: 47-68 kPa (14-20 in Hg) 5. Turn the ignition OFF. 6. If the engine vacuum reading is within the specified normal range, proceed to step 10. 7. If the engine vacuum reading is NOT within the specified normal range, inspect the engine vacuum hose for the following conditions: Loose connection to the engine Collapse, deformation or contamination Cracks, cuts, dry-rot 8. If any of these conditions were found with the engine vacuum hose, replace the hose, then IMPORTANT: Engine temperature, accessory load, and elevation level Vacuum readings will decrease by approximately 2.7
2008 Chevrolet Silverado 1500 2008 BRAKES Hydraulic Brakes - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
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