How do you replace thermostat on a 1997 Toyota Tercel?

To replace the thermostat on a 1997 Toyota Tercel, start by draining the coolant from the radiator and removing the upper radiator hose connected to the thermostat housing. Next, unbolt the thermostat housing, remove the old thermostat, and clean the mating surfaces. Install the new thermostat with the spring side facing the engine, reattach the housing, and reconnect the radiator hose. Finally, refill the cooling system with coolant and check for leaks.