Checking the performance of the brake booster (Mitsubishi Carisma)

A simple check of the brake booster operation is carried out as follows.

1. Run the engine for 1-2 minutes and turn it off. If the first time you press the brake pedal, it is pressed all the way down, and with subsequent presses, its travel gradually decreases, then the vacuum booster is working normally. If, with successive presses of the pedal, its travel remains unchanged, then the vacuum brake booster is faulty.

2. With the engine not running, press the brake pedal several times. Then, without releasing the 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 turn off the engine.

4. Keep the pedal pressed for 30 seconds. If the pedal position does not change, the vacuum booster is working properly.

5. If the pedal rises, the booster is faulty. If all three tests performed give satisfactory results, the booster can be considered to be working well. 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.