How can I fix my overcooling. The temperature gauge stays low, except when stopped in traffic ie traffic lights, then it will rise to the top end of the white square on the gauge, never goes up to normal.

Bernie Hamblett, December 2004

you can test the electricals by plugging in a spare sensor dipped in boiling water (at 90 degrees it should read half way on the gauge) just turn on ignition don't start the engine. It may be possible to use a carefully selected resistor/resistors .Try 96 ohms in series with 39 ohms (135 ohms) assuming it is a PT100 type sensor this will simulate 90 degrees Celcius.
If its the water coolant thermotat then check that you can undo its housing easily before you get a replacement stat. motor factors have stats for under £12, ford may charge you £30 but if the housing cant be separated a new housing complete with thermostat whether you need it or not is £40 from ford cant just get the thermostat housing!
It may be something else like your ECU software?

Emin Nesheli, October 2008

I have the same problem on a '98 1.8 LX petrol. I think the thermostat's stuck open and will need to replace it.

Joe, December 2004