One time, I was having fits trying to repair this exact problem, everything on the car was new and still once in a while the gauge went hot, slowly returning to normal.
After a couple days of pulling what was left of my hair out, the service manager brought a bulletin, not a service bulletin but just a managers eyes only engineers notice about a few cars coming through like this. It was just a ground resistance equation and took 5 minutes to fix, is the coolant level ok? It may be the thermostat sticking or its low on coolant, even the fans that cool it may be bad or their controls, air in the system from a leaking head gasket, all will cause this also, it may just be the sending unit circuit also.
Tuesday, January 5th, 2010 AT 7:51 PM