DOE Quality Parts | Radiator Caps
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DOE Radiator Caps Are Manufactured To Original Equipment Quality.

When quality and integrity matter most.

The radiator cap is a component of the radiator and cooling system. The car’s radiator performs a heat exchange function by transferring excess heat from engine coolant to the air. When coolant heats, it expands under pressure.

The radiator cap acts as a pressure valve, to release pressure at maximum pressure. Maximum pressure is usually 10 kPa, and when it is exceeded, the valve is forced open, the heat escapes and the excess coolant flows to the tanks on each side of the radiator. When the pressure level and heat has returned to a certain level, the radiator cap valve will close, and any coolant in the overflow tank will be returned to the cooling system.

Important: never handle the radiator cap after the car has been driven as it will be very hot. Allow the engine to cool down first.

The radiator cap is easily accessible because coolant needs to be topped up on a regular basis. It’s important to remember to replace the cap once you have topped up with coolant, otherwise it will leak out.

How do you know if your radiator cap is faulty?

Sometimes an overheating radiator, or low levels of coolant, may be due to a faulty radiator cap.


Low coolant levels

It is normal for coolant levels to drop over time, and the level should be checked every time you fill up with petrol. If the coolant light continues to stay on after you have topped your coolant level up, it may be a sign of a faulty radiator cap. Inspect the cap for signs of coolant leakage.

Collapsed radiator hoses

Collapsed radiator hoses may indicate a faulty radiator cap.


Premature overheating can occur because of the radiator’s inability to release heat and pressure.

Tips For Purchasing A Radiator Cap


Radiator caps are available in a variety of pressures, first determine which cap is suitable for your vehicle. Consult your local spares shop if you are unsure.

Allow the engine to cool down before unscrewing and replacing the cap to top up coolant.

Always ensure it fits correctly, and securely.