How to Change Your Car's Thermostat

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

Difficulty: Moderate

Instructions

Things You'll Need:

• English and metric ratchet set or open-ended wrench set
• Flat-blade screwdriver
• Pliers
• Workmen’s gloves
• Spray lubricant
• Putty knife or scraper
• Emery Cloth
• New Thermostat
• Gasket
• Gasket sealant

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

2. 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.

3. 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.

4. 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.

5. 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.

6. 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.

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

8. 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.

9. 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.

10. 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.

11. Replace the thermostat cover and screw the bolts in place.

12. Replace the radiator hose.

13. 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.

14. 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.

15. Check the coolant level and replace what is needed.

Tips & Warnings

• Clean up any spilled coolant immediately. Cats love the sweet taste and the coolant will kill them.
• 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.
• Never open the radiator cap when the engine is hot. The hot, pressurized coolant can cause severe burns.
• 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.

Resources

• How Stuff Works – How a Car’s Thermostat Works
• Integra.orcon.net.nz – How to Change the Thermostat
• Jonko Online Auto Repair – How to Change the Thermostat

[ASPolicastro]

on 6/16/2009 Hi Ken,
Excellent point about the hoses and clamps. Everyone should do that.

Hi Kathy,
I'm so glad I was able to help you with this article.

[kenl123]

on 6/16/2009 It would be a good idea to check the condition of the hose and consider replacing it. You may also need new hose clamps, especially if the old ones are crimped on or rusty.

[katvando]

on 8/16/2008 Thank you for this web page. I am a 42 year old widow who just fixed her thermostat with only the help of your instrutions. Thank you so much, Kathy from MI