How do you change the thermostat on a 1994 Buick Century?

To change the thermostat on a 1994 Buick Century, start by ensuring the engine is cool, then disconnect the negative battery cable. Drain the coolant from the radiator, and remove the thermostat housing by loosening the bolts. Take out the old thermostat, clean the mating surfaces, and install the new thermostat with the correct orientation (usually with the spring side facing the engine). Finally, reassemble the housing, refill the coolant, and reconnect the battery.