How to change the thermostat in a 2003 Ford Focus?

Answer 1

Procedure:

1) Let engine cool down for at least 1 hour before beginning.

2) Follow the instructions in this article to drain the cooling system

3) Un-plug the coilpack wiring harness. The retaining clip is on the bottom of the plug. Press it upwards while pulling the plug toward you. (see diagram below)

4) Unbolt the EGR tube brackets with a 13mm socket and a 10mm open-end wrench (see diagram below)

5) Push the EGR tube down a little bit to give you working room to access the bolts on the thermostat housing 5a (optional) I remove the battery and the battery case to allow more room to have for a work space.

6) Using pliers, squeeze the clip on the upper hose, and slide it away from the end of the hose. Release pressure on the clip, then pull the hose straight away from the thermostat housing to remove it. (see diagram below)

7) Using the ratchet and a 10mm deep well socket, remove the 3 bolts holding the thermostat housing to the cylinder head. Use a finger ratchet if needed. (see diagram below)

8) Using pliers, squeeze the clip on the rear hose, and slide it away from the end of the hose. Remove this hose the same way you removed the hose in step 6.

9) Once the rear hose is removed, you can push the thermostat housing -- still attached to two more hoses -- down and under the hard, black A/C tube. This will help you remove the remaining two hoses on the front of the thermostat housing. Again, remove these hoses the way you did in steps 6 and 8. The housing will be completely removed at this point. You can see the damaged housing in the picture below. This is very common:

10) Using a TORX T25 driver, remove three the screws attaching the thermostat retainer.

11) Pull the thermostat out of the housing.

* During re-assembly, you will need to re-use the old thermostat and thermostat retainer. The new housing does not come with these parts.