Simply put, the cooling system helps regulate the amount of heat in the engine. If it's too hot, the engine can overheat. If it's too cold, the engine emits more pollutants and engine components prematurely wear out. If the cooling system fails to keep the engine at the right temperature it can suffer significant damage and in some cases fail entirely.
Although a few cars are air-cooled, most modern vehicles use liquid cooling. Here are the critical components in liquid-cooled systems.
Coolant or antifreeze performs two critical functions. It keeps the radiator fluid from freezing in wintry conditions and keeps the engine from overheating in warm weather. Coolant is composed of 50 percent ethylene glycol and 50 percent water, which helps raise its boiling point and lower its freezing point. Corrosion inhibitors protect vital metallic cooling system components from corroding and silicates lubricate seals. There are different kinds of antifreeze, which are most easily identified by their color. How do they differ?
The radiator is a heat exchanger with hundreds of individual tubes and fins that reduce the temperature of the coolant. As coolant travels through the engine passageways it absorbs and removes heat from the engine transporting it to the radiator. Air flows through the coolant passages as the car moves, cooling the tubes and fins and coolant reenters the engine with a reduced temperature.
If you've ever worked on a car, then you know not to remove the radiator cap while the engine is warm. That's because the cap is a pressure-release valve. It keeps the cooling system under pressure in order to increase the boiling point of coolant.
The engine/radiator fan can be driven by a drive belt or an electric motor. It helps cool a car when it's stationary or moving slowly.
The thermostat helps the engine reach operating temperature by preventing coolant from circulating to the radiator, thus allowing the engine to heat up more quickly. As the engine reaches operating temperature, the thermostat opens and allows coolant to flow through the radiator.
The water pump circulates coolant through the system via an impeller (a rotor that spins to move fluid), which is driven by a belt.
The heater core is a smaller version of the radiator and located underneath the dashboard. A motor blows air past the heater core, which transfers heat to the air. This keeps cabin occupants warm, even in winter.
In addition to keeping the engine cool, on cars with an automatic transmission, the radiator is equipped with a separate heat exchanger to keep transmission fluid from boiling over.
If your car is leaking coolant, immediately determine from where and how much. If it continues to leak, schedule your car for service as soon as possible. An overheating cooling system can destroy the engine.