Usually found in larger vehicles such as SUVs and trucks and some rear wheel drive vehicles, the viscous fan is a thermostatic apparatus that is part of the vehicle cooling system. The main function of the cooling system is to keep the engine cool and stop it from overheating. The viscous fan plays an important role in enabling the engine to function as efficiently as possible and to perform at its best.
The viscous fan can be found in the crankshaft pulley or another of the accessory pulleys and spins around in the space between the radiator and the engine, sucking air back into the radiator and then blowing a stream of air across the engine. This air, though absorbing some heat as it travels through the radiator, is significantly cooler than the surface of the engine it is passing above, enabling the engine to be cooled by the air flowing above it.
The viscous fan operates with a viscous coupling which works with a bi-metallic sensory process, very much like a thermostat does. The viscous fan functions to pull more ambient air through the radiator when the temperature of the engine rises, then blows this air over the surface of the engine which lowers the temperature of the liquid coolant travelling through the engine.
A faulty viscous fan will mean that the engine is losing one of the vital cooling processes. A viscous fan can get stuck fast, which means it will be in operation even when not needed which leads to loss of engine power and has an adverse effect on fuel economy. A malfunctioning viscous fan can also lead to problems with the air conditioning system because the viscous fan functions to cool the AC condenser. Damaged bearings can cause the engine to produce a grinding noise. When you need to replace this part, specifically designed for the make and model of your vehicle, a good quality viscous fan is the ideal compatible part.