How to change a zetec thermostat

Updated July 20, 2017

The Zetec engine is used in smaller Ford vehicles such as the Focus and the Festiva. The engine uses the thermostat to regulate the flow of coolant in and out of the engine. When the engine starts to get hot, the thermostat will release coolant in to the engine. Replacing the thermostat requires removing the whole assembly to access the thermostat. Always replace the coolant with fresh coolant to ensure the engine stays cool at all times.

Open the bonnet for access to the engine compartment. Locate the radiator at the front of the engine compartment. Place a drain pan under the radiator.

Locate the drain valve at the bottom of the radiator with a crescent wrench. Allow all the coolant to drain out. Close the drain valve when the coolant is gone.

Locate the EGR tube bracket on the left side of the engine. It will be sitting next to the air filter assembly. Unscrew the retaining bolts and push it downward slightly. This will allow more room to work.

Squeeze the hose clamp at the end of the radiator hose where it is attached to the engine. Pull the hose off the intake pipe. Pull the hose at the back of the housing the same way.

Unbolt the three bolts with a socket wrench. Pull the top off the thermostat housing. Pull the thermostat housing up slightly to reveal two more hoses at the bottom. Disconnect those hoses by loosening the hose clamps and pulling the hoses off the piping.

Pull the whole thermostat housing out of the engine compartment. Locate the three screws in the housing and undo the screws with a Torx screwdriver. Pull the retaining ring out of the housing. This will free the thermostat to be pulled out. Replace with the new thermostat.

Push the retaining ring back in to the housing. Secure in place with the three retaining screws.

Position the housing back in to the engine compartment. Attach and tighten the two hoses to the bottom of the housing by squeezing the tabs until the clamp is over the piping and the hose.

Replace the o-ring on the thermostat housing with a new o-ring. It will be included with the new thermostat. The o-ring will sit at the top of the thermostat housing cover.

Bolt the thermostat housing cover down with the socket wrench. Tighten the three screws with a socket wrench.

Position the two hoses on to the housing. Squeeze the clamp and ensure it is over the pipe and the hose. Release the clamp to secure the hose. Repeat for both hoses.

Unscrew the radiator cap by hand. Pour in a gallon of pre-mixed coolant. Do not place the cap back on to the radiator.

Start the car and allow it to idle. Pour more coolant in until it is full. Tighten the cap back on to the radiator. Turn the car off.


Contact a recycling centre for disposal of the waste coolant.

Things You'll Need

  • Socket wrench
  • Socket set
  • Torx driver set
  • 2 gallons of Pre-mixed coolant
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About the Author

Gregory Crews has been in the film industry for three years and has appeared in more than 38 major motion pictures and 16 television shows. He also writes detailed automotive tutorials. His expertise in the automotive industry has given him the skills to write detailed technical instructional articles.