Originally Posted by
christph
No, no one way valve. It just relies on the principle that hot water rises and cold water sinks. When I first got it I wondered if it would actually circulate, and it does. The hot water rises from the front of the head to the top of the radiator, and the cooler water flows from the bottom of the radiator to the back of the head. The temperature difference between the hoses is significant. After doing some research I learned early cars and tractors worked on the same principle--they didn't have water pumps.