The thermostat is not serviced separately. The thermostat and housing must be replaced as an assembly.Disconnect negative battery cable.Remove engine cover (Refer to 9 - ENGINE COVER - REMOVAL) .Partially drain cooling system (Refer to 7 - COOLING - STANDARD PROCEDURE).Disconnect upper radiator hose and bypass hoses at thermostat housing (2) .Remove thermostat housing retaining bolts, support bracket and housing from cylinder head, discard gasket.