Radiator caps seal off the radiator and pressurize the coolant inside, raising its boiling point. They are essential to a properly functioning cooling system.
If the radiator cap goes bad a few things can happen. Typically the pressure seal will be lost which will both cause the coolant to boil at a lower temperature and allow coolant to escape from the cap. This can result in a dramatic spray of liquid coming from the radiator accompanied by a great deal of steam.
Replacing the radiator cap is a very easy fix, just remove the old and repalce it with a new one. Just be sure to never remove it while the engine is hot!
We stock and sell a wide variety of quality radiator caps from these manufacturers: