The main function of the aluminum radiator cap is to release excess water or pressure when the cooling system expands due to the increase in temperature and pressure; it flows into the auxiliary tank, and when the temperature of the cooling system is low, the auxiliary tank is re-opened through the aluminum radiator cap. The water is sucked back into the cooling system, so that it can keep the water volume of the cooling system without water shortage when the temperature is high or low.
The other is that the aluminum radiator cap has a fixed pressure value. The water is not easy to boil under high pressure. It is easy to boil at low pressure. Boiling will produce air. Therefore, the aluminum radiator cap can maintain a constant pressure in the system and use high pressure to make it boiling. Increase the heating efficiency, and the purpose of the radiator with pressure is to prevent the water from boiling, so that it can dissipate heat more effectively.