Car Care: How to Replace a Thermostat

Save a big repair bill with this simple fix

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.

By the DIY experts of The Family Handyman Magazine

TIME

One day

COMPLEXITY

Simple

COST

Under $20

Replacement procedure

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.

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Required Tools for this Project

Have the necessary tools for this DIY project lined up before you start—you’ll save time and frustration.

  • Socket/ratchet set
  • Rags

You'll also need hose-clamping pliers, a plastic scraper and a drip pan

Required Materials for this Project

Avoid last-minute shopping trips by having all your materials ready ahead of time. Here's a list.

  • T-stat
  • Gasket
  • RTV sealant
  • Coolant