A car thermostat is mounted in the cooling system and regulates the temperature of the coolant. The thermostat stays closed to stop the flow of coolant when the engine is cold. This allows the engine to warm up to operating temperature much quicker. When operating temperature has been reached, the thermostat opens, allowing the coolant to circulate to keep the engine from overheating. A faulty thermostat can cause your engine to run too hot or too cold.
Turn off the engine and open the hood. Allow the engine to cool for several hours so that you will not be burned by scalding coolant.
Place a clean drain pan under the drain valve of the radiator. Open the valve a few turns counterclockwise with a wrench. Do not remove the valve. Allow the coolant to drain into the pan. Close the valve with the wrench when the coolant has drained. Remove the drain pan from under the vehicle and place it aside.
Locate the upper radiator hose on top of the engine. Follow the hose from the top of the radiator to the thermostat housing on the engine block. Loosen the hose clamp from the end of the hose that is attached to the thermostat housing with a flat blade screwdriver. Slide the clamp down the hose and away from the housing. Twist the hose off of the housing and push it aside.
Remove the thermostat housing retaining bolts counterclockwise with a socket and ratchet. Place the bolts aside. Remove the housing from the engine block. Scrape any gasket residue from the mating surface with a gasket scraper.
Lift the thermostat straight up and out of the thermostat housing. Push a new thermostat into the housing until it is fully seated. Make sure the new thermostat is placed into the housing using the same orientation as the old thermostat.
Place a new thermostat housing gasket onto the mating surface. Place the housing back over the engine block, making sure the mounting holes in the engine block line up with the gasket and the housing. Replace the retaining bolts and tighten with a socket and ratchet. Push the radiator hose back onto the housing until it is fully seated. Slide the hose clamp back into its original position and tighten it with a flat blade screwdriver.
Remove the cooling system filler cap and place a large funnel into the opening. Pour the coolant from the drain pan back into the funnel. Replace the cap and start the engine. Let the engine reach operating temperature and check for leaks. Close the hood.
