Why do some radiators not have a cap?
Why do some radiators not have a cap? The cooling system is a pressurized system and it is rated at a specific pressure. 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. What to do if your car runs without the radiator cap on? On top of your Thermostat Housing, there may be a small fitting, it's an air bleed valve. If it's there, open the bleed valve, til no more...