What Does Radiator Fluid Do? Definition, Meaning and Concept

Radiator fluid, commonly called coolant, is responsible for several tasks in a vehicle. Cooling the vehicle's engine is just a function of the fluid in the radiator. The automatic transmission in a vehicle has its hydraulic fluid cooled by fluid from the radiator, and the engine's water pump is also lubricated by the flow of coolant through the pump. In winter, in cold weather areas, the coolant also provides heat to the vehicle by flowing through a smaller radiator known as the heater core. As the engine heats the fluid in the cooling system, a small fan blows across the heater core, drawing hot air into the vehicle's passenger compartment.

While water can be used as a radiator fluid, it is not recommended for typical use as it does not work as efficiently as manufactured coolant, commonly known as antifreeze. Antifreeze is manufactured not only to prevent the radiator fluid from freezing during the cold winter, but also to absorb heat. Doing so cools the engine much better than water alone.

On diesel engines, a heater is commonly installed in the engine block or lower radiator hose to allow the radiator fluid to stay warm while the engine is not running. This helps the engine start easier in cold weather by warming the oil and keeping it thin and fluid. It also heats the combustion chambers to increase engine starting efficiency.

In hot summer weather, radiator fluid keeps the engine cool by passing through a radiator. The radiator is a series of cooling tubes or ducts with a thin metal fabric, called fins, between the tubes. The coolant flows through the tubes while the heat in the coolant is dissipated in the fins.

The cooling fan draws air from outside the engine compartment through the radiator fins to cool the fluid. The radiator also has reservoirs on each side or bottom, depending on the type of radiator. Automatic transmission lines send transmission fluid to be cooled by fluid from the radiator.

As the hot transmission fluid enters the radiator, the radiator coolant absorbs the heat and allows the transmission fluid to return to the transmission much cooler than it left off. The transmission fluid actually flows through a hard steel line that runs through the U-shaped radiator tank and out of the radiator to couple with the fluid lines from the transmission. On some turbocharged and supercharged engines, air from the turbo or supercharger passes through an intercooler, a type of radiator that uses fluid from the radiator to cool the incoming air charge and create more horsepower.