Hyundai 59110-25030 Booster Assembly-Brake

Start the engine and depress the pedal to ensure it goes down slightly. Then, depress the brake pedal multiple times with the engine running and check for any changes in the pedal reserve distance. Start the engine and turn it off after a minute or two, and depress the brake pedal slowly. If the pedal goes down farther initially but gradually rises after subsequent depressions, the booster is airtight. 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 it for 30 seconds, the booster is airtight.