Coolant Reservoir Cap Pressure

But they do a lot more than just that.

Coolant reservoir cap pressure.

Caps are designed to ensure that the prescribed pressure on the cooling system is maintained at all times during operation by allowing air to escape in case of overpressure. The radiator cap and expansion tank cap make sure the filling hole of the radiator and expansion tank are sealed off gastight. Coolant goes into the reservoir tank as it expands. If the coolant reservoir cracks or breaks due to old age or overheating it will leak.

Another symptom of a potential problem with the coolant reservoir is coolant leaks. If you have a bad radiator cap the coolant could get released too quickly and cause the reservoir to overflow. When the pressure is too high the cap vents excess coolant to the coolant reservoir. While you re in there check to make sure your coolant overflow tank is working properly.

The radiator cap releases the extra pressure by sending some coolant into the overflow tank. The radiator cap actually increases the boiling point of your coolant by about 45 f 25 c. The cap is actually a pressure release valve and on cars it is usually set to 15 psi. Cutaway of radiator cap and reservoir.

A reservoir is under pressure in normal circumstances in order to increase the coolant s boiling point. How does this simple cap do this. In case of a faulty radiator cap the required pressure fails to build up inside the system leading to overheating. If your cap isn t venting this causes excess pressure in the cooling system and can cause leaks or a collapsed radiator hose.

At operating temperature coolant can evaporate from the open system.