Testing and cleaning a clutch fan

January 1, 2011 | By Richard Prince


I purchased a 7-blade clutch fan for my 1963 Imperial from an Arizona salvage yard donor car. What should I do to clean it up before I install it and make sure it will work?


A thermostatic fan clutch is designed to increase or decrease fan speed in accord with engine temperature. As the temperature increases, the coupling force within the clutch mechanism increases, causing the fan to turn faster and thereby move more air through the radiator and across the engine. When the temperature decreases, the coupling force diminishes to the point where it releases and thereby disengages the fan from the engine.

If the fan clutch you’ve bought has obvious signs of fluid leakage then it’s probably not going to work correctly. If there’s discernible play between the two halves of the clutch, namely the half that the fan bolts to and the half that bolts to the drive pulley, then the clutch should not be used.

If it’s dry and feels tight, the easiest way to test it is by installing it onto your engine and seeing how it performs. When the engine is cold and the clutch is cold, fan speed should not increase proportionately when engine speed increases. When the engine and fan clutch are hot, the fan should turn in sync with the engine.

If you want to media blast the fan clutch to improve its appearance, then you should thoroughly seal the joint where the shaft enters the thermostat housing. This is easily done by cleaning the area with solvent and then wrapping it with several layers of heavy duct tape.