I've got a mk3 TDDI mondeo as my daily runabout and it had the typical symptoms of a thermostat opening too early, took ages for the heaters to get warm, temperature gauge would rise to normal when booting it but when driving steady it would drop off to 1/4 or lower. It has never over heated and the cooling fans cut in and out as normal when left idling.

I changed the thermostat today and it is still not coming up to temperature as it should, it is definately better than it was as it comes up to normal operating temperature without needing to drive it as hard however when coasting or on light throttle it is still dropping off to nearly bugger all and the heaters are getting cold.

Any ideas as to what could be going on? It runs fine and uses no oil or water.

Cheers