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Air Tightness (With Gauges)

  1. Start the engine and keep it running until a vacuum of 19.69 in Hg. (66.7 kPa) is indicated on vacuum gauge. DO NOT depress the brake pedal.
  2. Stop the engine and watch the gauge. If the vacuum drop range is less than 0.98 in Hg. (3.3 kPa) within 15 seconds after stopping the engine, the brake booster is functioning properly. If defective, the cause may be one of the following:
    • Check valve malfunction.
    • Leak from vacuum hose.
    • Leak from the shell jointed portion or stud bolt welded portion.
    • Damaged diaphragm.
    • Leak from valve body seal and bearing portion.
    • Leak from plate and seal assembly portion.
    • Leak from poppet valve assembly portion.
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