Abstract: The viscous fluid coupling is comprised of a drive shaft having a hollow casing rotatably mounted thereon with one end of the drive shaft extending into the hollow casing. The interior of the casing is divided into a reservoir chamber and an operating chamber by means of a dividing plate secured within the housing. The rotor on the end of the shaft is rotatably mounted within the operating chamber and a thermostatically responsive valve member is rotatably mounted within the reservoir chamber for controlling the flow of fluid through a first passage extending through the divider plate. A centrifugally responsive valve member is located within the divider plate for providing additional control of the fluid through the first passage from the reservoir chamber to the operating chamber.