The cooling system is a pressurized system and it is rated at a specific pressure. This pressure is regulated by the radiator cap which is designed to vent pressure that exceeds what the maximum limits are. The limit is written on your radiator cap i.e. 13psi 15 psi. when a cooling system is tested for leaks, it is pressurized to the limit on the radiator cap. Then observed for leaks that can be found under pressure. Air cooled and electric cars do not have radiator caps.

All liquid cooled cars have a radiator cap. On late model cars with sloped hoods the car makers install the cap on the expansion tank mounted on the fender.

You don't mention make, model, or year. Technically, cars with surge tanks don't have a radiator cap, they have a pressurized recovery tank cap. Same purpose, just a different layout.

Unless it's an electric car, it has a radiator cap. It may not be on the radiator though. It may be on the coolant reservoir tank.

Stpaulguy, Billy and Pat the non-mechanics are wrong again. Many cars and trucks have the *cooling system pressure cap directly on-top of the pressurized coolant recovery reservoir.

What's the year make and model of your car or truck and we'll give you the part number of the cooling system pressure cap and where it is.

we need to know the vehicle for this q first. ill bet that it has one but it may not be what you are thinking. newer cars have it on the over flow tank in a full flow system.

The car is a: NISSON CALIFORNIA 1990 MODEL. It was not sold in the: USA