How do you change a thermostat for 2004 Mitsubishi diamante?

To change the thermostat on a 2004 Mitsubishi Diamante, first, ensure the engine is cool and disconnect the negative battery cable. Drain the coolant from the radiator and remove any components obstructing access to the thermostat, such as the upper radiator hose. Unbolt the thermostat housing, remove the old thermostat, and clean the mating surfaces before installing the new thermostat with a new gasket. Finally, reassemble everything, refill the coolant, and check for leaks.