2002 Buick Century thermostat

Drain the coolant system, and then disconnect the uper radiator hose and remove the thermostat housing. Next take out old thermostat clean the mating systems between housing and hose and put in new thermostat and gasket. Then reconnect the housing and the hose, fill up the radiator and bleed it of air.

Here is the correct way to change out the engine cooling system thermostat. Check out the images (below). Let us know if you need anything else.