Cars & Vehicles Auto Parts & Maintenance & Repairs

How to Test a Radiator Cap

    • 1). Allow the system to cool and remove the cap. Inspect the seal for damage. Heat cycling of the seal hardens the rubber, and split seals are a common source of leaks. Damaged seals require replacement of the radiator cap. Other damage, such as bent or broken recovery valves (the recovery valve is a disc shaped piece in the center of the cap.) and rusted springs require replacement of the cap.

    • 2). Install the cap onto the radiator cap adapter supplied with the tester set. This adapter looks like a radiator filler neck on both ends. Install the cap on one end, and attach the other end of the adapter to the pressure tester. There are several different sizes and shapes of radiator cap, and several sizes and shapes of adaptors. Select the adapter that is the same shape as the radiator filler neck on your specific vehicle.

    • 3). Pump the pressure tester to the pressure stamped on the radiator cap. If the pressure releases the pressure before reaching the correct pressure, or the cap does not hold pressure, the cap is faulty. Remove the cap from the adapter, and reinstall it on the adapter. Repeat the test to verify that the cap is faulty.

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