How to Replace a Car’s Thermostat

If your car is running hotter than normal conditions, then this is mostly a result of the wearing out thermostat. Here are steps to replace a car’s thermostat. Follow the directions.

Things Needed

  • New Thermostat
  • Gasket sealant
  • Gasket
  • Emery Cloth
  • Putty knife or scraper
  • Spray lubricant
  • Workmen’s gloves
  • Pliers

Car's Thermostat

  • Flat-blade screwdriver
  • English and metric ratchet set or open-ended wrench set


Step 1:

Visit a local auto parts dealer and buy a new good thermostat, gasket sealant and gasket for the particular model of your car.

Step 2:

The radiator cap has to be removed, before removing, a thick rag like a bath towel has to be placed over the radiator cap and slowly start turning it while listening to the pressure being released. When the hissing stops, completely remove the cap!

Step 3:

Find the two inch black hose exceeding out from the top of the radiator. The hose will be clamped onto the thermostat cover ending somewhere on the top of the engine. The thermostat cover contains two bolts on each side.

Step 4:

The hose has to be removed using pliers or a screwdriver, the clamp needs to be pulled off. Stainless steel clamps with a screw are used by some manufacturers while some use a clip clamp.

Step 5:

The hose has to be twisted for loosening it from the thermostat cover. If the hose is difficult to loosen, use the spray lubricant. Be cautious that some coolant will pour out from the hose when it is taken off.

Step 6:

Use an appropriate sized open-ended wrench or ratchet socket to loosen the two bolts on each side of the thermostat cover. Remove the thermostat by lifting the cover off.

Step 7:

Remove the old gasket from the thermostat cover and cover base by using a putty knife or scraper.

Step 8:

Sand away any of the remaining traces of the gasket with an emery cloth. It should be made sure that the cover base and cover are clean and smooth or the cover will leak.

Step 9:

Use the spring mechanism to drop down the new thermostat into the engine. There is a narrow recessed area at the point where the top of the thermostat fits itself.

Step 10:

The gasket sealant has to be spread on the thermostat’s cover that makes contact with the engine and the cover base. The gasket has to be placed on the cover base and make sure that the bolt holes are lined up.

Step 11:

The thermostat cover can be replaced now and the bolts can be screwed properly.

Step 12:

Replace the radiator hose.

Step 13:

Before starting the engine, allow the gasket sealant to dry. Consult the sealant package for directions and check how long the sealant takes to dry properly.


Step 14:

When the sealant has dried, start and run the engine until the engine reaches its normal working temperature. Inspect the hose and thermostat cover to make sure that there are no leakages.

Step 15:

In the end, check the coolant level and refill if necessary.

Tips and Precautions

  • Any spilled coolant should be immediately cleaned. It is dangerous especially for cats.
  • The radiator cap should be NEVER opened when the engine is hot. The hot and pressurized coolant can result in serious burns.
  • If the thermostat bolts are hard to remove and are rusted, then bolt-freeing lubricant can be used for loosening them. The bolts can break if they are forced.
  • Only the correct thermostat and gasket should be purchased for the car. In case they don’t properly fit, exchange it from the auto parts store where you got it. The size of the gasket will always be larger than the cover and will be overlapping it.