Checking the operation of the brake booster (Mitsubishi Pajero 4)

A simple check of the brake booster operation is performed as follows:

1. Start the engine for one or two 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 the pedal travel remains unchanged after successive presses, the 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, after starting the engine, the pedal remains in place, then the vacuum booster is faulty.

3. With the engine running, press the brake pedal and then turn off the engine. Keep the pedal pressed for 30 seconds. If the pedal position does not change, the vacuum booster is working properly. If the pedal rises, then the amplifier is faulty. If the results of one of the tests performed are unsatisfactory, then you should look for a fault in the vacuum hose, check valve or brake booster.