Brake Booster Operating Test

For simple checking of the brake booster operation, carry out the following tests:

1. Run the engine for one or two minutes, and then stop it. If the pedal depresses fully the first time but gradually becomes higher when pressed succeeding times, the booster is operating properly. If the pedal height remains unchanged, the booster is defective.
   Fig 1: Brake Booster Operating Test (1 of 3)

   Courtesy of HYUNDAI MOTOR CO.
2. With the engine stopped, step on the brake pedal several times. Then step on the brake pedal and start the engine. If the pedal moves downward slightly, the booster is in good condition. If there is no change the booster is defective.
   Fig 2: Brake Booster Operating Test (2 of 3)

   Courtesy of HYUNDAI MOTOR CO.
3. With the engine running, step on the brake pedal and then stop the engine. Hold the pedal depressed for 30 seconds. If the pedal height does not change, the booster is in good condition. If the pedal rises, the booster is defective.
   Fig 3: Brake Booster Operating Test (3 of 3)

   Courtesy of HYUNDAI MOTOR CO.

If the above three test are okay, the booster performance can be determined to be as good. If even one of the tests is not okay, Check the check valve, vacuum hose, and booster for defects.

VACUUM HOSE (CHECK VALVE) 

Inspection

1. Disconnect the brake booster vacuum hose (check valve built-in) (A) at the booster (B).
2. Start the engine and let it idle. There should be vacuum available. If no vacuum, the check valve is not working properly. Replace the brake booster vacuum hose and check valve, and retest.
Fig 4: Vacuum Hose
Courtesy of HYUNDAI MOTOR CO.