Replacement Radiator Caps

For every 1-psi increase in cooling system pressure, the boiling point of the coolant will raise approximately 3 degrees. For example, with water only (distilled is recommended as it will not cause corrosion to cooling system parts) and no radiator cap, the boiling point will be approximately 212 degrees Fahrenheit. Adding a 16-psi radiator cap will raise the boiling point to 252 degrees Fahrenheit and with a 50/50 mix of water and coolant, the boiling point will be further raised to 267 degrees Fahrenheit. At this temperature engine damage will result. Therefore, there is no benefit to obtaining a higher boiling point with a higher pressure cap. It is important to understand that you should only use the pressure rating recommended by your vehicle's manufacturer or 16 lbs for older vehicles with American V8 engines. If the pressure is too high, any weakness in the cooling system will be revealed with a leak, loss of connection (such as a clamp), or part failure.

Adding a decorative radiator cap or cap cover to your radiator completes the level of detail to your cooling system and engine bay. Whether polished, chrome-plated, or with a custom logo, a radiator cap enhances the look of your radiator or overflow tank.

Yes, auto radiator caps work. They contain a spring and seal that is rated in pounds (lbs). System pressure under the cap rating results in a closed off seal. When the cooling system pressure reaches the rating on the radiator cap, the valve in the cap opens and excess coolant escapes from the radiator to a recirculating or recovery tank through at fitting in the radiator neck. For each psi raised in the cooling system, the boiling point is raised by three degrees (for example, a 16 lbs cap will raise the boiling point 48 degrees). This helps avoid coolant boil-over that can lead to component damage from higher coolant temperatures.

The two most common locations that a radiator cap can be found are the top corner of the radiator or the recirculating / overflow tank. Older vehicles usually have the radiator fill cap directly on the radiator, while late-model vehicles have the cap on the overflow tank.

The steps on how to test a radiator cap are simple with the help of a tester. A radiator cap cooling system test kit will help you confirm if you have a radiator cap leak and if it is properly working by applying pressure to it along with a gauge reading. If the gauge reading matches the rated pressure on the cap, the cap is working properly. If the radiator cap is leaking when installed and it's been confirmed that it is properly connected, the seal is bad and the cap needs to be replaced.