Thanks mate, yeah its a cheap part but nearer 20 quid which is still ok. I just replaced the one above the gearbox and I have the same problem, the thermostat has also been done which only leaves the 2nd sensor to check (which I can't find). This leads me to believe the 1st sensor still works and the 2nd is dodgey. But they could also both be dodgey. I just want to see if I can test the 1st one before buying another.