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How to Replace a Car Thermostat

Suketu Mehta

The car thermostat needs replacement, when it wears out due to excessive usage. Check the instructions for replacing it.
A failure of any car part, however small or big, can result in your vehicle coming to a halt all of a sudden, even when in motion. One such small and often neglected part is the thermostat. This part is present in between the radiator and engine.
It is basically a temperature controlled engine coolant valve. Your car's cooling system goes for a toss in case this part stops functioning, leading to engine overheating and the car being not being able to move.
The thermostat controls the flow of coolant to the radiator. When internal combustion starts, heat is generated inside the cylinders, which is invariably absorbed by coolants present in the passages.
The thermostat's role is to let the coolant pass only when the engine has reached its usual operating temperature. Once the process begins, hot coolant from the engine is brought in to the radiator, where it cools off and within a few seconds, it travels back to the engine to soak in more heat.

Tools Needed

  • A wrench (open-ended)
  • Pliers or a screwdriver
  • Lubricant
  • Scraper or putty knife
  • Gloves
  • Piece of emery cloth
Apart from this, you will also have to purchase a new thermostat, gasket, and gasket sealant, according to the particular brand and model of car you own.

Replacement Procedure

Step 1

Cover the radiator cap with a thick bath towel and start turning it, while you hear the pressure being released. As soon as the noise ceases, take out the cap completely. You will now have to find the thermostat.
Look for a black colored hose, about 2 inches in size, emerging at the top of the radiator. It will be fixed on the cover of the engine's surface, with the help of two bolts on either side.

Step 2

Use pliers or a screwdriver to unscrew the hose and take off the clamp at the engine. It could be either a clip clamp or a steel clamp depending upon the car. Turn the hose around at the cover to loosen it up.
Note that there will be some amount of coolant which will come out when you remove the hose. Use a wrench to relax bolts on either side from the cover. Raise the cover and take the thermostat out.

Step 3

With help of a scraper, take out the old gasket on the cover. Take an emery cloth and wipe off any traces remaining. Using the spring mechanism, simply put down the new thermostat into the engine. Apply gasket sealant on it. Cover where it touches the engine. Fix the new gasket on the cover in such a manner that all bolts are aligned in a straight line.

Step 4

You will now have to change the old cover with the new one. Also, change the radiator hose. Start your car engine only when the sealant is totally dried. Let the engine run for a while till it reaches its usual operating temperature. Examine the new cover and hose for any signs of leakage. Also, check coolant levels and make replacements if necessary.


The cost of replacing a car thermostat usually ranges between $100 and $300.
Thus, replacing the thermostat can conveniently be done at home. It will take you about an hour and does not cost much either. Regularly check for faulty parts in your car and replace them if necessary, to ensure optimum performance and long life of the car.