There are two cooling systems in a car or truck. One has to do with the driver and we call that one air conditioning. The other is to keep the engine cool and that is the one that is the topic of this post. The Engine Cooling System consists of the the radiator up front behind the grille, the hoses from the radiator to and from the engine, the hoses to and from the radiator to the heater (known as the heater core) inside the car, and other items including the thermostat. The thermostat sits between the radiator and the engine, most often on the engine and regulates the flow of coolant through the system. It opens and closes by means of a spring which expands and contracts from the heat of the coolant. The typical coolant temperature of most vehicles is around 180 degrees F. Boiling is around 200 degrees. Since the system is sealed by a radiator cap that allows the system to become pressurized,