GM 20812025 Power Brake Booster ASSEMBLY

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To perform an operating check on the power brake booster, start by depressing the brake pedal multiple times with the engine off to ensure there is no change in the pedal reserve distance. Then, depress the pedal and start the engine to see if it goes down slightly, indicating normal operation. For an air tightness check, start the engine and turn it off after a minute or two. Slowly depress the brake pedal several times and observe if it goes down farther the first time but gradually rises after the second or third depression, indicating an airtight booster. Alternatively, depress the brake pedal while the engine is running and then stop the engine with the pedal depressed. If there is no change in the pedal reserve travel after holding the pedal for 30 seconds, the booster is airtight. If a problem arises with the power brake booster, it cannot be rebuilt and must be replaced with a new one. To remove the booster, disconnect the battery cable, remove the master cylinder, disconnect the vacuum hose check valve, and remove the driver's side lower trim panel in the passenger compartment. If necessary, remove the cover from the underhood fuse/relay box, the underhood electrical center, and the transmission control module. Then, remove the clip or nut and bushing securing the booster pushrod to the brake pedal arm, and detach the pushrod from the pedal arm. Remove the booster-to-firewall mounting nuts and guide the booster unit away from the firewall. Retrieve the gasket if it is not stuck to the booster. To install the booster, place it into position with a new gasket and tighten the retaining nuts to the specified torque. Lubricate the pushrod pin on the brake pedal arm with multi-purpose grease, connect the pushrod to the brake pedal, and install the clip. Reconnect the vacuum hose, install the master cylinder, and bleed the brakes. Finally, reconnect the battery and thoroughly test the brake operation before putting the vehicle back into normal service.