You can have a big problem with your little Ford Focus if the thermostat is not working correctly. Fortunately for Focus owners, Ford has made changing the thermostat a relatively quick, painless procedure. In less than an hour, you can be back behind the wheel of your Ford Focus.
Make sure the engine of your Ford Focus is cool. Use jack and jack stands or wheel ramps to raise the front of your Focus. Turn radiator cap about 1/4-turn to release pressure in the cooling system. Remove cap when hissing stops, indicating pressure is relieved.
Locate radiator draincock on the passenger-side of the bottom of the radiator, facing the rear of the Focus. Attach a hose to the plug if desired to minimize coolant spillage. Loosen the plug to drain coolant into a suitable container. Reuse coolant if relatively new and clean.
Press the retaining clip on the bottom of the coilpack wiring harness upwards while pulling the plug toward you to unplug the harness. Use a 10mm open-end wrench and a 13mm socket to remove the bracket holding the exhaust gas recirculation (EGR) tube. Push EGR tube down to access thermostat housing.
Use pliers to loosen the clip at the engine-end of the upper radiator hose where it meets the thermostat housing. Pull the hose off the housing. Take out two bolts holding housing cover and remove cover.
Note the position of the old thermostat. Pull out the old thermostat and seat new thermostat into thermostat housing in the same position. Clean any residue from inside the housing cover. Place new gasket over the thermostat and replace housing cover.
Reattach radiator hose, EGR tube and bracket and the coilpack wiring harness. Refill the radiator with reserve or new coolant. Start your Focus and allow the engine to warm up. Check for leaks.
Do not attempt to drain coolant when the car engine is hot.