Radiators and the Cooling System
Cars have a cooling system for two main reasons: to maintain a safe engine temperature, and to heat up the water used in the heating system. The radiator is a key component of the cooling system. It regulates the temperature of the engine by removing excess heat. This is accomplished by the circulation of coolant throughout the engine block and radiator. If the radiator doesn’t work, the car will be in danger of overheating.
The operation of a radiator is fairly simple. The engine’s coolant (basically a mixture of water and ethylene glycol, otherwise known as antifreeze) passes through tubes within the hot engine block and heats up. It then flows through a rubber tube into the inlet tank at the top of the radiator.
The coolant circulates through the core of the radiator, a series of small tubes. The tubes are surrounded by thin, flat fins that increase the surface area inside the radiator, which increases the heat exchange. The hot coolant flows around the core and heats the fins, which are then cooled by the air flowing through the vehicle. In part, the fins are cooled by the air that passes through the engine as the car is moving, but there is also a fan to keep air circulating. The coolant is now cooler, and it flows back into the engine to be reheated: the cycle begins again.
The pressure within the radiator is maintained by a spring-mounted cap. If the engine is off and the car is cold, there is no pressure in the radiator. When the coolant heats up, it expands, and the cap is pushed outward slightly as the pressure increases. If the pressure gets too high, the cap will allow some of the excess coolant to flow into an overflow reservoir, so a healthy level of pressure is maintained within the radiator. Later, when the car cools down, the coolant will be drawn back into the radiator.
The most common radiator problems are leaks, clogs, and corrosion. If coolant leaks out through a crack or a hole, the engine can overheat. Similarly, when dirt or rust clog the radiator and prevent the flow of coolant, the engine can overheat. There is no air in a pressurized cooling system, which diminishes the risk of these problems. If the car is involved in an accident, the radiator fins may be damaged or bent, which can also diminish the performance of the cooling system. Finally, in some cases the thermostat that controls the flow of coolant becomes damaged, so the radiator is less effective.