GM 22707256 Power Brake Booster Assembly

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To perform an operating check on the brake system, 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, checking for a slight downward movement of the pedal, which indicates normal operation. For an airtightness check, start the engine and turn it off after a minute or two. Slowly depress the brake pedal several times, noting if it goes down further on the first depression but gradually rises on subsequent depressions, indicating an airtight booster. Additionally, depress the brake pedal while the engine is running and then stop the engine while keeping the pedal depressed. If there is no change in the pedal reserve travel after holding it for 30 seconds, the booster is airtight. If removal of the power unit is necessary, it is recommended to use special tools and have a new or factory-rebuilt unit installed. To remove the unit, start by removing the master cylinder and, if applicable, the hydraulic control unit on ABS-equipped vehicles. Disconnect the vacuum hose check valve and remove the driver's side lower trim panel. Remove the clip and retaining pin securing the booster pushrod to the brake pedal arm. Inside the engine compartment, remove the bolts securing the brake booster to the mounting bracket and carefully guide the unit out. To install the booster, place it into position and tighten the retaining bolts to the specified torque. Connect the pushrod to the brake pedal and install the clip. Install the master cylinder and reconnect the vacuum hose. For ABS-equipped models, reposition the hydraulic control unit and secure it with mounting nuts. Finally, bleed the brakes and thoroughly test the brake operation before returning the vehicle to normal service.