How to Change Your Car's Thermostat

by braniac

If you notice your car's engine is running hotter than usual, it is often a result of the thermostat wearing out.

Go to your local auto parts store and purchase a new thermostat, gasket and gasket sealant for your particular make, year and model car.

Open the radiator cap, but before you do, place a thick rag like a bath towel over the cap on the radiator and slowly turn it while listening for the pressure to be released. When it stops remove the cap completely.

Locate the thermostat by finding the two-inch thick black hose coming out of the top of the radiator. The hose will end somewhere on the top of the engine and it will be clamped onto the thermostat cover. The cover will have two bolts on each side.

Remove the hose by using the screwdriver or pliers to pull off the clamp. Some auto manufacturers use stainless steel clamps with a screw and some use a clip clamp.

Twist the hose to loosen it from the thermostat cover. Use the spray lubricant if the hose is difficult to loosen. Be aware that a considerable amount of coolant will pour out of the hose when you take it off.

Loosen the two bolts on each side of the thermostat cover with the appropriate-sized ratchet socket or open-ended wrench. Lift the cover off and remove the thermostat.

Use the putty knife or scraper to remove the old gasket from the thermostat cover and cover base.

Use an emery cloth to sand away any remaining traces of the gasket. Make sure the cover and cover base are smooth and clean or the cover will leak.

Drop the new thermostat with the spring mechanism down into the engine. Notice there is a narrow recessed area where the top of the thermostat fits.

Spread the gasket sealant on the thermostat cover that makes contact with the engine and on the cover base. Place the gasket on the cover base, making sure the bolt holes line up.

Replace the thermostat cover and screw the bolts in place.

Replace the radiator hose.

Wait for the gasket sealant to dry before starting the engine. Read the directions on the sealant package to determine how long the sealant needs to dry.

When dry, start the engine and run it until it reaches the engine's normal operating temperature. Check the thermostat cover and hose to make sure there are no leaks.

Check the coolant level and replace what is needed.


  • check Clean up any spilled coolant immediately. Cats love the sweet taste and the coolant will kill them.
  • check Make sure you purchase the correct thermostat and gasket for your car. If they don't fit, go back to the auto parts store and get the right one. The gasket will always be a bit larger than the cover and will overlap it.


  • close Never open the radiator cap when the engine is hot. The hot, pressurized coolant can cause severe burns.
  • close If the thermostat bolts are rusted or difficult to remove, use bolt-freeing lubricant to loosen them. Forcing the bolts may cause them to break.

Items you will need

About the Author

This article was written by the It Still Runs team, copy edited and fact checked through a multi-point auditing system, in efforts to ensure our readers only receive the best information. To submit your questions or ideas, or to simply learn more about It Still Runs, contact us.

Photo Credits

  • photo_camera Photo by Anthony S. Policastro