If the heater is giving a good supply of hot air when the temp is high I would suspect a clogged radiator. How many miles has it done?

This saga runs and runs !!!....So far my very reputable and normally excellent garage have changed the thermostat (twice with different makes) the thermostat housing, water pump, temperature sensor, AND the radiator...and nothing makes any difference!

They have flushed it through thoroughly and pressure tested it, and all seems fine. At the moment I am running around without a thermostat, and fillled with tap water, and behaves perfectly ...BUT.. as soon as you put the thermostat back it, and put your foot down, it overheats. Somehow, even with the middle knocked out of it, the mere presence of the thermostat stops the ciruclation to the expansion tank.

The garage have admitted defeat, and given it back to me for the time being without the stat in it, whilst they consult with Ford and try and come up with another plan of attack

I'd change the b***** car if I could afford to, but as I can't, suggestions are still welcome.

It doesn't rise and fall really quickly in the way a rev counter does. It starts off fine, and is OK for the daily commute of 20 mins varying between 30-60mph. But get on the motorway for while at cruising speeds and it slowy climbs right up into red. Dropping back to 50mph will see the temp needle fall back after around 5-10 seconds to about the 3/4's point, but it won't drop below this until the engine has stopped and cooled right down. Speed up again, and the needle quickly climbs back to the red.

Never loses a drop of coolant.

It does none of this however when you take the thermostat out, but circulates water and behaves perfectly normally... But this is not an all year round solution of course!

Garage is adamant that coolant is not circulating when the the thermostat is fitted, but have apparently changed and checked all the associated parts 2 or 3 times, and cannot say why.

Edited by RedLake on 28/07/2011 at 21:43