Pressure/Filler Cap Test
- Park the vehicle on a level surface, set the parking brake, and chock the wheels. Open the hood.
- After the coolant has cooled, loosen the pressure/filler cap to relieve system pressure.
- Remove the pressure/filler cap. Using the Snap-On tool radiator-cap tester shown in Table., check the pressure relief cap to see if it maintains pressure to within 10% of the pressure rating marked on the cap. If it does not, replace the cap. Make sure that the replacement radiator cap is correctly rated for the cooling system of the vehicle. Use the recommended tool in Table..
- Inspect the pressure/filler cap gaskets. Replace the cap if the gasket shows any signs of deterioration or damage. Install the cap and check that the cap seals properly on the surge tank filler neck. Replace the cap if it appears not to seat properly.
- There is a valve on the bottom of the pressure/filler cap that opens under vacuum. This prevents components in the cooling/heating systems from collapsing. Inspect the vacuum-relief valve to be sure it is not stuck. Replace the cap if the vacuum-relief valve is stuck.
Warning: Do not remove or loosen the radiator cap until the engine and cooling system have completely cooled. Use extreme care when removing the cap. A sudden release of pressure from removing the cap prior to the system cooling can result in a surge of scalding coolant that could cause serious personal injury.
Notice: The radiator cap currently installed may not be the same one installed when the vehicle was built. If the radiator cap must be replaced, make sure that it is the correct cap for the cooling system of the vehicle. Because the radiator cap pressure rating affects the operating temperature of the engine, installing an improperly rated radiator cap may have adverse effects on the cooling system, and engine operating temperatures. This could cause premature engine wear or damage.