it can yes i have heard the same romor.

awesome, i might have to get my car dropped off at the mechanics and get it checked out...ill post the results

thanks for all the replies but the problem with all of them is that before i cahanged the old thermostat with exactly the same setup, none of this was ever a problem. the cap is only 6 months old and in good nick. does anyone know the resistance of the temp sender at operating temp?

The cap on my xh was only 6 months old too..........

if the dash cluster is digital, there's a very good chance that it's just the gauge playing up, they are notorious for it, mine doesnt play up though.

Gab

Tip about hoses was good one. Bottom rad hose should have a coil of wire in it to stop it being sucked in by pump when running mid to high revs.
If rad is partially blocked then this problem is made worse.
With cold motor reach down and squeeze bottom rad hose to see if there is resistance to crushing and also check that the wire is not flattened out like our Ford badge.
The only difference between recovery and non recovery rad caps is the washer under the cap lid.
Also check that thermostat is not in wrong way around, I have managed to do this on one occasion and it gives this exact symptom!
Good hunting.