Thermostat replacement

Mark 3 Ford Mondeo Thermostat Change

Symptom: car takes a more than a few minutes to produce lots of hot air on a cold winters day.

Thermostats always fail in the open position. In the old days it cost 5 quid and took 5 minutes to change. On the mark 3 it has fancy electronics, costs 90 quid and the garage will quote you 300 quid to fit it. It’s a terrible location behind the power steering pump.

It took me hours to work out how to do it. However, once you know how, you can change it in one hour and save yourself a fortune. You will need the following tools. Don't attempt it without these.

1, An angled pair of GrooveLock Pliers/grips for removing the rubber hose clips.

2, A miniature ratchet set such as the Stanley 18 Piece Micro Tough 1/4" Ratchet Set. Google this item so that you know what it looks like. It costs about 20 quid and you absolutely must have the universal joint.

3, A telescopic magnetic pick up tool. I got mine as part of one of those cheap tool kits you pick up at motorway service stations. You will need it if you drop one of the bolts or your socket down into an inaccessible place. Believe me, this is quite likely.

Method:

Open bonnet.

Remove the plastic grill in which the key hole is located.

Unplug the headlamp unit at the back.

Pull up a retaining pin at either side of the headlamp to free the unit.

Remove the headlamp unit.

Use the pliers to squeeze the large hose clip and work it off the end of the hose. Except for putting it back on you have now completed the hardest part of the job.

Remove the large hose. This releases a couple of liters of coolant.

Now there are three bolts holding the thermostat to the engine block.

Use an 8 mm socket on the long extension to remove the top right bolt. You can just see it looking down a crack from directly above.

Use the socket on the universal joint on the long extension to remove the bottom right bolt. You will have to feel for this one.

Use a 10 mm socket to remove the nut that holds the power steering pump tube bracket to the engine block. Rotate the bracket a few degrees to the left to free up the access rout (very little movement needed).

Use an 8 mm socket on the long extension to remove the top left bolt and remove thermostat. You will be able to see this bolt through the headlamp hole through which you have been working. This releases more coolant.

Remove the small hose using the pliers.

Remove the electrical connection to the thermostat by pressing down on top and pulling it off.

Throw the old thermostat over your shoulder.

Clean any baked on rubber gasket from the mounting face on the engine block. I found my thumb nail was most effective.

The new thermostat is fitted by reversing these steps with one exception. You do not need to reconnect the electrical connector until after the thermostat is fitted. It pushes on very easy because you don’t have to release it by pushing down on top.

The important thing to note when refitting the thermostat is that you connect the small hose first. Then bolt the unit onto the engine. Make the electrical connection. Connect the big hose. The most difficult bit is getting the big hose clip back on. I held the clip open using the angled pliers and pushed on the opposite side with the edge of a ring spanner.

If you follow these instructions you will complete the job in an hour, if you know some mechanics.

Even quicker if you have small hands.

If you drop a bolt and you do not have the telescopic magnet tool you will have to turn the car upside down and give it a shake.