A: To check the vacuum booster operation, start the engine and depress the pedal to ensure it goes down slightly. For the airtightness check, start the engine and turn it off after a minute or two. Slowly depress the brake pedal several times and observe if the pedal goes down farther initially but gradually rises after subsequent depressions. For the hydraulic booster, turn off the engine and depress the brake pedal several times to deplete the pressure in the accumulator. If the booster is functioning properly, the brake pedal will sink towards the floor and then rise back up against your foot. To remove the booster, deplete the pressure in the accumulator (for hydraulic booster) or detach the vacuum hose (for vacuum booster). For hydraulic booster, detach the pressure and return lines, cap them to prevent fluid leakage, and carefully remove the master cylinder without detaching the Brake Lines. For vacuum booster, remove the master cylinder. Remove the pushrod retaining clip bolt (if present) and the pushrod retaining clip, then slide off the Brake Light Switch and pushrod from the pin. Finally, pull the booster and gasket from the engine compartment. To install, use a new gasket and tighten the booster and master cylinder mounting nuts to the specified torque values. If working with a hydraulic booster, bleed the power steering system and check the fluid level.