The radiator cap is made up of 2 valves, a pressure valve and a relief valve.

The function of the radiator cap or the expansion tank cap is to regulate the internal pressure in the cooling circuit.

The radiator cap is a special cap consisting of a 2-way valve and a pressure relief valve. The cap controls increasing pressure as the coolant heats, and allows coolant to flow back into the radiator as the engine cools.

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