Replacing a Car Thermostat: Step-by-Step Instructions

Do-It-Yourself Car Thermostat Replacement

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.

Step 1: Remove the Old Thermostat

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.

Step 2: Clean Both Mating Surfaces

Next, use a plastic scraper to remove the old gasket and any sealing compound, cleaning both the engine and the gooseneck sealing surfaces. Dry the surfaces with a rag.

Step 3: Install the New Thermostat and Gasket

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, placing 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. 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.

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