Is Yo Landy overheating?

Hope there's someone out there who can help ...

My 1990 90 TD temp gauge zooms straight to red and beyond after a brief warm up and I can't seem to get to the bottom of the problem. I've changed the sender ... no result ... and I've changed the thermostat... no result ... what do I do next?

She's not boiling over at all, in fact the header tank stays relatively cool ...

Any ideas welcome ...

could be the temp gauge, but unlikely. maybe a wiring problem.

temp gauge grounding problem. try clean the connectors first. if that fails swap out the gauge and see.

Thanks for the advice ... I'll let you know how I get on. If it was a short wouldn't it just whack straight over and stay there rather than bounce about round the red?

I had the same problem, replaced the sender and stat and then found that it was a wiring/earthing problem to the temp guage - had a mobile electrician rewire the guage - he also found the relay to the rear heated screen was missing and after sorting, the temp guage has been fine.