A radiator cap functions as a heat exchanger. It transfers excess heat from the engine's coolant fluid into the air. The pressure of the cap can vary depending on the engine application, from 13 to 16 psi. The radiator cap also allows the engine's coolant to expand and contract without allowing a lot of air to enter the cooling system. Apart from this, another big role of a radiator cap is that is allows the coolant to flow back into the radiator as the engine cools. Cars with automatic transmissions cool transmission fluid in the same way with a separate heat-exchange circuit built into the radiator. If you'd like to take a look at our vast range of radiator caps, make sure to visit the category on eWorldTrade. eWorldTrade is a business to business portal that aims to connect businesses globally. eWorldTrade focuses on providing their clients with the best products and services at the lowest wholesale rates possible and of the highest quality. At eWorldTrade, you can directly inquire from the manufacturers that meet your requirements and for feedback or additional help, you always have our customer support