GM 84472897 Power Brake Booster ASSEMBLY

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To check the vacuum booster, start the engine and depress the pedal to ensure it goes down slightly. Then, depress the brake pedal multiple times with the engine running to check for any changes in the pedal reserve distance. For the airtightness check, start the engine and turn it off after a minute or two. Slowly depress the brake pedal multiple times and observe if the pedal goes down farther the first time but gradually rises after subsequent depressions. Additionally, depress the brake pedal while the engine is running and 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. For the hydraulic booster, turn off the engine and depress the brake pedal several times to deplete the pressure in the accumulator. Then, push down on the brake pedal with approximately 40 pounds of force and start the engine. If the booster is working properly, the brake pedal will sink toward the floor and then rise back up against your foot. If the booster does not work as described, check the fluid level in the power steering fluid reservoir and inspect the hoses for kinks. If everything is fine, the booster or power steering pump may be defective and the power steering pump output pressure should be checked. To remove the booster, disconnect the negative battery terminal, deplete the pressure in the accumulator or remove vacuum, detach the vacuum hose or pressure and return lines, and remove the master cylinder without detaching the brake lines. Disconnect any electrical connectors and remove the pushrod from the brake pedal arm, followed by the four nuts holding the brake booster to the firewall. Slide the booster out from the firewall and remove it along with the gasket. For installation, use a new gasket and tighten the booster and master cylinder mounting nuts to the proper torque specifications. If working with a hydraulic booster, bleed the power steering system and check the fluid level.