Acura 46400-S47-J51 Power Assembly, Master (8"+9")

To check the airtightness of the brake booster, start the engine, turn it off after a minute or two, and depress the brake pedal slowly several times. If the pedal goes down farther the first time but gradually rises after subsequent depressions, the booster is airtight. Also, depress the pedal while the engine is running, then stop the engine with the pedal depressed; if there is no change in pedal reserve travel after 30 seconds, the booster is airtight.

To check the brake booster: Start the engine with the brake fully depressed, and the pedal should move down slightly. Depress the brake pedal several times, and the travel distance should not change. Stop the engine and hold the pedal in for about 30 seconds; the pedal should neither sink nor rise. Restart the engine, run it for about a minute, and firmly depress the brake several times; the pedal travel should decrease with each application. If the brakes do not operate as described, the brake booster has failed.