The cooling system of your car is one of the most important parts, without one your engine would be useless in minutes. Many people change the cap for esthetic reasons alone, and while we like things to look good, there has to be a more important reason. What does the radiator cap do? Other than the most apparent reason, allowing you to fill your radiator, the radiator cap is an essential part of the system. As the coolant gets hot, it expands creating pressure inside of the system, and when it reaches a certain point, this pressure is then released through the radiator cap plunger into an overflow tank. Once the pressure has dropped below the desired level the plunger inside of the cap will close.
So why should you upgrade your radiator cap? Increased pressure in your cooling system can increase the boiling temperature. By upgrading to a stronger cap, you can effectively raise the boiling temperature of your system, reducing the risk of having your coolant turn into steam which then will cause cavitation. Cavitation, or air pockets, will prevent the coolant from actually cooling the engine which can result in extreme wear and damage vital engine parts. The OEM cap is rated at 1.1bar and the Hybrid Racing cap is rate at 1.3 bar!