Checking the operation of the brake booster (Mitsubishi Lancer 9)

1. Start the engine, let it run for one or two minutes, and then turn it off. If the first time you press the brake pedal, it presses all the way down, and its travel gradually decreases with subsequent presses, then the vacuum booster is working properly. If its travel remains unchanged with successive presses of the pedal, then the vacuum brake booster is faulty.



2. With the engine not running, press the brake pedal several times. Then, without releasing the brake pedal, start the engine. If the brake pedal drops slightly, the vacuum booster is working properly. If the pedal remains in place after starting the engine, the vacuum booster is faulty.



3. With the engine running, press the brake pedal and then turn off the engine. Keep the brake pedal pressed for 30 seconds. If the brake pedal position does not change, the brake booster is OK. If the brake pedal rises, the brake booster is faulty.





4. Analysis of inspection results.

a) If the results of all three tests are positive, then the operation of the brake booster is normal.

(The material was borrowed from the website MitsubishiMan)

b) If the results of one of the tests performed are unsatisfactory, then the fault should be looked for in the vacuum hose, check valve or brake booster.