How to Replace the Thermostat in a Ford Focus

Written by paul vaughn
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Changing a car thermostat is relatively easy as long as the diagnosis has already been done and you have determined that the problem is the thermostat. There are many causes of overheating in a vehicle that should be checked before changing a thermostat. If you have determined that the thermostat needs changing, use the following steps to safely remove it, replace the gasket between the thermostat and the input hose, and reattach the hose.

Skill level:
Moderately Easy

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Things you need

  • Safety glasses
  • Work gloves
  • Large flathead screwdriver
  • Open-end box-end wrench
  • Ratchet and socket set (optional)
  • Gasket scraper
  • New thermostat flange gasket
  • New thermostat

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  1. 1

    Allow the car to cool for at least 2 hours before attempting this procedure. The coolant in the system is extremely hot and can cause second- and third-degree burs in seconds if the wrong line is opened.

  2. 2

    After the engine is cooled, use your open-end box-end wrench or ratchet and socket set to remove the plastic covering over the return line of the coolant system.

  3. 3

    Use your large flathead screwdriver to slowly loosen the input clamp on the return line. There should be no pressure on this line, but think safety first. Once the clamped is loosened, used the screwdriver to loosen the return line from the thermostat output flange.

  4. 4

    Remove the return line from the thermostat input line. Remove the two bolts on either side of the thermostat housing flange. Use your wrench or ratchet and socket set.

  5. 5

    Use a gasket scraper to remove the old gasket between the thermostat housing and thermostat flange. Make sure all of the old gasket is removed, or the new one will leak. Pry the old thermostat loose, and remove. Put the new gasket in place, and then the new thermostat. Re-secure the flange bolts with your wrench or ratchet and socket set. Plate the return hose back in place over the thermostat. Tighten the clamp with your screwdriver.

Tips and warnings

  • You may need a new return hose depending on how long the hose has been in place. They tend to fall apart when you start prying on them if they are very old.
  • If you don't remove all the old gasket material, the new gasket will leak. Take the extra time so you don't have to buy another gasket later.
  • Wear gloves when handling the return line.
  • Safety glasses should be worn throughout the procedure.
  • Be very careful to let the engine cool sufficiently before starting the procedure.

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