Depending on the application, a radiator can either decrease or increase the temperature of the system it is employed in. It is common to use radiators to maintain warmth in homes during cold weather conditions. However, in automobiles, radiators are used to decrease the temperature of the engine. Similar to the steering fluid which forms a main component of the steering system, and the refrigerant which plays a key role in air conditioning systems, radiators use coolants to help attain and maintain the optimal temperature in the engine. The coolant is usually a mixture of water and ethylene glycol. The coolant also has other additives to prevent corrosion, erosion and cavitation in various engine parts.
Older vehicles used water to bring down the temperature of the engine. To improve the cooling performance in various temperatures, coolant were then introduced in automobiles. To endure the high and low climatic temperatures in which the vehicles are operated, coolants have high boiling points and very low freezing point temperatures.

The coolant, which flows around the various engine parts, is pumped by a centrifugal pump connected to the crankshaft. As the coolant flows through the passages in the engine, it takes heat away from it. The hot coolant makes its way out of the engine to reach the radiator. The radiator has a series of small tubes which allow the coolant to flow through them. To reduce the temperature of the coolant, air from outside is allowed to flow over the tubes in the radiator. For a more efficient cooling, a cooling fan also blows air into the radiator. Some radiators have turbulators within the tubes to enhance the cooling effect. The turbulence effect created by them ensures quick cooling of the coolant and the engine. The hot air from the radiator is let into the atmosphere.The coolant which is now at a normal temperature again flows to the engine to repeat the cycle all over again. This process continues as long as the engine is running. Radiators, which were originally constructed from copper and brass, are now usually made of aluminum and plastic. Radiators are usually located behind the vehicle's grille. It is not necessary for the radiators to be employed all the time. Only after the engine attains a preset temperature, the radiator starts working. For this purpose, a thermostat is included in the radiator to monitor the temperature in the engine. Below this preset temperature, the coolant will not flow through the engine nor will the radiator work.