Pressure Relief Cap Check
Warning: Do not remove or loosen the surge tank 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.
Caution: 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.
- Remove the fill cap first, to relieve the cooling system pressure, then remove the SAE cap.
- Using a radiator-cap tester, check the pressure cap to
see if it maintains pressure to within 10% of the pressure rating
marked on the cap. If it doesn't, replace the cap. See Fig. or Fig.. Make sure that the replacement radiator cap is correctly rated
for the cooling system of the vehicle.
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Low-Coolant-Level Sensor
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SAE Cap (for coolant overflow pressure relief only)
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Fill Cap
Fig. 1, Surge Tank, Century Class Conventional
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Radiator/Charge Air Cooler Assembly
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Fill Cap
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Surge Tank
Fig. 2, Surge Tank, Argosy COE
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- There is a second valve in the radiator cap that opens under vacuum. This prevents the collapse of hoses and other parts that are not internally supported when the system cools. Inspect the vacuum-relief valve to be sure it is not stuck.
- Make sure that the cap seals properly on the coolant filler neck seat, and that the radiator cap gasket is not damaged. On vehicles with screw on caps with O-rings, make sure that the O-ring is not cracked or deteriorated. Replace the cap if the gasket shows deterioration or damage.