Air Tightness Check

Fig. 6 Booster Air Tightness Check:

1. Start engine and stop after one or two minutes.
2. Depress brake pedal several times slowly. If pedal drops the most the first time, but gradually rises after the second or third time, booster is air tight, Fig. 6.
3. Depress brake pedal with engine running, then while depressing brake pedal, stop engine. If there is no change in pedal reserve travel after holding pedal for 30 seconds, the booster is air tight.