Replacing a car's thermostat (or T-stat) is an easy and inexpensive repair, and in most cases will cure an overheating or no-heat problem, sparing the time and expense needed for expert diagnostics.
Pry off the gooseneck. Then remove the thermostat from the engine or the inside of the gooseneck.
Use a plastic scraper to remove the old gasket and any sealing compound. Then dry the surfaces with a rag.
Place the new thermostat in the recessed groove in either the engine or gooseneck (air bleed toward the top). Hold it in place with a self-adhesive gasket. Then apply a bead of RTV sealant.
In most cases, the cause of an overheating or no-heat condition in your vehicle is a faulty thermostat. And since a new “T-stat” costs only about $8, it makes more sense to replace it than to spend hours diagnosing the problem. If that doesn't fix it, at least you're only out about two hours.
Pick up a new T-stat and gasket, as well as RTV sealant, fresh coolant (to top off the system) and hose-clamping pliers at an auto parts store. And while you're there, ask the clerk for the torque specs for the gooseneck bolts. Then gather up your metric sockets, a plastic scraper and a drip pan. Slide the drip pan under the engine to catch the spilled coolant.
The T-stat is usually located near the top of the engine under a “gooseneck” housing attached to the upper radiator hose. If yours isn't there, consult a shop manual to locate it. Remove the two or three bolts that hold the gooseneck in place and remove the T-stat (Photo 1). Next, clean both the engine and the gooseneck sealing surfaces (Photo 2). If the parts store gave you a plain gasket, coat one side with RTV sealant (self-adhesive gaskets don't need sealant). Then install the T-stat and gasket (Photo 3). If the old T-stat used a rubber O-ring instead of a gasket, lubricate the new one with fresh coolant before you insert it. Reinstall the gooseneck and top off the coolant.
Have the necessary tools for this DIY project lined up before you start—you’ll save time and frustration.
You'll also need hose-clamping pliers, a plastic scraper and a drip pan
Avoid last-minute shopping trips by having all your materials ready ahead of time. Here's a list.