how easy should a fan clutch spin
A fan clutch is supposed to be a fluid coupling device that allows the fan to rotate less than the engine speed. The fan clutch should engage before the engine gets up to 220F. A standard cooling system fan clutch should spin at 33% of water pump speed (RPM) when not engaged and 75% of water pump RPM when engaged. A heavy duty cooling system fan clutch should spin at 33% of water pump speed (RPM) when not engaged and 90% of water pump RPM when engaged. Unfortunately, a fan clutch can slowly empty its coupling oil overtime and often seizes. (the oil also can gel/thicken and grab).