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Testing The Pressure Cap

WARNING: This page is about a different car, the 2002 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.

TOOLS REQUIRED:

CAUTION: DO NOT REMOVE PRESSURE CAP FROM A HOT SYSTEM. ALLOW THE SYSTEM TO COOL, THEN SLOWLY REMOVE PRESSURE CAP.
  1. Remove the pressure cap from the coolant surge tank.
  2. Make sure that all parts of the pressure cap, tester, and adapter are clean.
  3. Wet the rubber gasket of the pressure cap with water and install Surge Tank Cap Tester J42401-1 to cap.
    Fig 1: Installing Surge Tank Cap Tester J42401-1 To Cap
    G01041176Courtesy of GENERAL MOTORS CORP.
    CAUTION: WEAR SAFETY GOGGLES.
    CAUTION: NEVER PUMP THE PRESSURE CAP ABOVE 138 KPA (20 PSI).
  4. Pump the tester, watch the pressure gauge, and read maximum pressure before the relief valve opens. Stop pumping. The pressure cap is rated at 138 kPa (20 psi).

    Cap opening pressure: 13-17 kPa (1.9-2.5 psi)

    Vacuum relief setting: 1.0 kPa (.1 psi) below atmospheric pressure

  5. Watch needle for 30 seconds to see if it falls. The needle should not fall below 68.1 kPa (10 psi).
    Fig 2: Testing Pressure Cap
    G01041177Courtesy of GENERAL MOTORS CORP.