Cayenne; w/o Turbo. A circular disk covered in rubber or plastic with a hole in The center where The edge is sometimes tensioned by a spRing that prevents fluid from leaking at The Engine Coolant Outlet Housing. Engine Coolant Outlet O-Ring. Engine Coolant Thermostat Gasket. Engine Coolant Thermostat Housing O-Ring. Engine Coolant Thermostat Seal. O-Ring. cover o -. Housing O -. outlt o -. Water Outlet. Gasket. Washer. Included with: Thermostat Housing.