An engine Cooling Fan draws cold air inside the engine bay by pulling through the radiator. It is either mechanical, electrical, or hydraulically driven. The cooling fan improves engine cooling, especially at idle low speed.
- Whenever the engine is cool or at its normal temperature, the fan clutch partially disengages the engine's mechanically driven radiator cooling fan generally mounted on the front of the water pump and driven by a belt and a pulley connected to the engine's crankshaft.
- If the engine's temperature rises above the clutch's engagement temperature setting, the fan becomes fully engaged, thus drawing a higher volume of ambient air through the vehicle's radiator, which provides to lower the engine coolant's temperature to an acceptable level.
Most of the fan clutches are viscous or fluid couplings, which are combined with a bi-metallic sensory system which is also similar to that in a thermostat. Some of the clutches are electronically controlled. These types of fan clutch are capable of providing the potential to control the level of engagement depending on any number of inputs.