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Component Tests: Cap

WARNING: This page is about a different car, the 2003 Ford Windstar. However, it is still accessible from the selected car via links, so may be relevant.
WARNING: Never remove the pressure relief cap under any condition while the engine is operating or when the cooling system is hot. Failure to follow these instructions can result in damage to the cooling system or engine and/or personal injury. To avoid having scalding hot coolant or steam blow out of the cooling system, use extreme care when removing the pressure relief cap from a hot degas bottle. Wait until the engine has cooled, then wrap a thick cloth around the pressure relief cap and turn it slowly (counterclockwise). Step back while the pressure is released from the cooling system. When certain all the pressure has been released, (still with a cloth) turn and remove the pressure relief cap.
  1. Remove the pressure relief cap from the degas bottle.
  2. Make sure the engine is cool.
  3. Wrap a thick cloth around the coolant pressure relief cap on the coolant reservoir. Slowly turn the cap counterclockwise (left) until the pressure begins to release.
  4. Step back while the pressure releases.
  5. When you are sure all the pressure has been released, use the cloth to turn and remove the cap.
  6. Immerse the pressure relief cap in water and install it on the shallow filler neck of the special tool.
  7. Immerse the filler neck seal in water and install it in the filler neck adapter.
  8. Install the filler neck adapter with the filler neck seal to the Radiator Cap Adapter.
  9. Connect the female quick-connect fitting of the pressure test pump to the male quick-connect fitting of the filler neck adapter.
    10. NOTE: If the plunger of the pump is depressed too fast, an erroneous pressure reading will result.
  10. Slowly depress the plunger of the pressure test pump until the pressure gauge reading stops increasing and note the highest pressure reading obtained.
  11. Release the pressure by turning the relief screw counterclockwise. Then tighten the pressure relief screw and repeat Step 6 (at least twice) to make sure the reading is repeatable within the specifications of the pressure relief cap.
  12. If the pressure test gauge readings are not within specifications, install a new pressure relief cap. If the pressure test gauge readings are within specifications, carry out the cooling system Pressure Test.
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