Check the operation of the brake servo without tester

Run the engine for a minute or two and then stop it. Repeatedly press the brake pedal is not with ordinary effort when braking. When you first press the brake pedal is squeezed it until it stops, and subsequent presses its course gradually decreases, the vacuum amplifier is operating normally. When repeatedly pressing the pedal its course remains unchanged, then the vacuum brake booster is defective (Fig. 6.3).

With the engine off, press several times on the brake pedal and make sure that the brake pedal travel is changed. Then, without releasing the brake pedal, start the engine. If the brake pedal is slightly lowered, it means that the booster is defective. If after starting the pedal remained in place, then booster is defective.

With the engine running, press on the brake pedal and then stop the engine. Hold the brake pedal for 30 seconds. If the pedal position does not change, then the vacuum brake booster is OK. If the brake pedal is lifted, then booster is defective (Fig. 6.4).

If the results of one of the checks carried out proved to be unsatisfactory, the problem should be sought in a vacuum hose, check valve and the brake servo.