Abstract: This disclosure deals with a drive for a fan of an internal combustion engine, the drive including a clutch connected between the engine and the fan blades. A piston is movable to actuate the clutch, and an actuating fluid is employed to move the piston. The fan drive is connected to the engine lubricating system so that the engine lubricant acts as the actuating fluid. An engine temperature responsive circuit actuates the clutch to engage and disengage at certain engine temperatures. The fan drive includes a fluid feed path, return path and control path, but only two fluid connections to the clutch are necessary. When the temperature responsive circuit operates to disengage the clutch, a valve releases the pressure in order to quickly disengage the clutch.