For a simple test of the operation of the vacuum booster, do the following.
1. Start the engine, let it run for 1-2 minutes and stop. Press the brake pedal several times with normal force. If the pedal goes down on the first press, but gradually rises on the second or third press, the brake booster is good. If the pedal height does not change, the booster is faulty.
2. With the engine off, press the brake pedal several times and check the change in pedal height. After that, press the pedal and start the engine. If at the same time the pedal goes down a little, the amplifier is working. If the pedal height remains the same, the booster is defective.
3. With the engine running, depress the brake pedal and stop the engine. Keep the pedal depressed for 30 seconds. If during this time the pedal height does not change, the amplifier is working. If the pedal rises, the amplifier is faulty.
If one of the above test methods reveals a malfunction, check the vacuum hose and booster and repair the malfunctions. If the test results are positive, the amplifier is OK.