Before any repairs, it is important to check the coolant level and drive belt tension, and make sure the temperature gauge or warning light circuit is functioning correctly. If the engine has overheated, there may be issues with cylinder head gaskets, pistons, or cylinder heads. To replace the thermostat, disconnect the negative battery cable, remove the engine splash shield, and drain the cooling system. Remove the engine cover and, if applicable, the throttle body cover and air cleaner housing. Disconnect and remove air pump hoses if necessary. Remove the radiator hose, housing mounting nuts, and the housing and thermostat assembly. Clean the sealing surfaces, install a new gasket, and reassemble the components in reverse order. Refill the cooling system, check for leaks, and ensure proper operation.