4.0 LITER. Thermostat unit o-ring. Engine Coolant Thermostat Gasket. Engine Coolant Thermostat Housing O-Ring. Engine Coolant Thermostat Housing Seal. Engine Coolant Thermostat O-Ring. O-Ring. Part cannot be reused/reinstalled. Housing O -. hsng o -. unit o -. Gasket. Included with: Thermostat, Thermostat unit.