The parts that make up the cooling system are the water pump, radiator, radiator cap, thermostat, cooling fan, coolant and all associated hoses. The water pump pushes coolant, which is a mixture of distilled water and antifreeze, through the cooling channels in the engine block and cylinder head(s). Once the coolant reaches a certain temperature the thermostat begins to open and sends coolant out of the engine to the radiator where it is cooled and brought back into the engine via the water pump. Normal operating temperature for modern engines is 190 degrees to 210 degrees Fahrenheit. In order to keep the water from boiling, the radiator cap pressurizes the system and raises the boiling point of the water. Modern cars are also equipped with computer controlled cooling fans. Typically, when the thermostat opens and coolant is pushed through the radiator, the computer turns the fans on in order to draw cool air across the radiator.