Checking the performance of the vacuum brake booster

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

1. Start 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, and with subsequent presses its stroke gradually decreases, then the vacuum booster is working normally. If, with successive pressing of the pedal, its stroke remains unchanged, then the vacuum brake booster is faulty.

2. With the engine off, press the brake pedal several times. Then, without releasing the pedal, start the engine. If the brake pedal is slightly lowered, then the vacuum booster is working. If, after starting the engine, the pedal remains in place, then the vacuum booster is faulty.

3. With the engine running, depress the brake pedal and turn off the engine.

4. Hold the pedal down for 30 seconds. If the position of the pedal does not change, then the vacuum booster is working.

5. If the pedal rises, then the amplifier is faulty. If all three tests carried out give satisfactory results, the performance of the amplifier can be considered good. If the results of one of the tests carried out were unsatisfactory, then a malfunction should be sought in the vacuum hose, check valve or brake booster.