The radiator cap keeps your engine cool by sealing and pressurizing the coolant inside. It is designed to hold the coolant in the radiator under a predetermined amount of pressure. Once the pressure reaches its maximum, the cap opens the release valve and allows heat to escape. To maintain your cooling system, it’s important that even the smallest components are working properly. If coolant is not moving effectively throughout the system and your car is overheating, have your service advisor check the radiator cap. A new radiator cap is an inexpensive repair and can prevent future damage. A malfunctioning radiator cap will cause the coolant to boil, and your engine will not get the proper amount of coolant. If ignored long enough, the engine will overheat, leading to costly repairs. From a safety standpoint there is a slight risk, because an overheated engine might leave you stranded. There is high environmental impact, because leaking coolant is harmful for children, pets and other animals.