Automobile Coolant System
The purpose of your engine's cooling system is to maintain the engine's internal temperature for optimum performance and efficiency.
Radiator
The radiator is usually positioned toward the front of the vehicles engine compartment. The radiator is a series of tubes which heated coolant is forced through. An engine driven fan is usually placed at the rear of the radiator to draw air through the radiator reducing the temperature of the coolant. Some cars will use electric fans to push or pull air through the radiator but no matter what set up is used it is to accomplish the same result of cooling the fluid circulated throughout the engine.
Radiator Cap
The cooling system is designed to operate under pressure. Pressure is maintained by the use of a radiator cap. The radiator cap has a sping that helps seal a gasket to close off the system. If the pressure in the system becomes greater than the springs tollerance then the gasket will un-seat releasing the access pressure.
Coolant Recovery System
The coolant recovery system is a (usually made of plastic) reservoir used to hold the coolant released by the radiator cap when the system goes over pressure. When the system cools back down the back pressure inside the cooling system will then draw the access coolant back into the main system flow.
Engine Coolant
Commonly referred to as "anti-freeze," engine coolant is usually a water-ethylene glycol mixture that will maximize cooling efficiency and protects against corrosion at the same time preventing freezing down to temperatures of about -20 degrees fahrenheit and below.
Engine coolant should be replaced every couple of years because, as with just like everything else, it wears out!
Thermostat
The thermostat is a valve placed in the cooling system to ensure a minimum operating temperature is maintained. When the coolant temperature is below the minimum the thermostat will restrict the flow to the radiator. As the temperature rises it will begin to open to increase the flow to the radiator, both the radiator and thermostat work together to maintain optimum engine temperature ensure best preformance.
Water Pump
The water pump is a pump which forces water through the cooling system.