I've got a Ford Mustang GT '97 4.6 V8. I don't know if that helps, but here's my issue.
Withing a few miles, the needle on the temp gauge will go all the way from the lowest point to between the "A" and "L" in the word "NORMAL" on the gauge. Well, in the past few days the needle is almost horizontal, going past the "HOT" indicator. There's no smoke. There's no gurgle. There's no performance issues. It's clearly not overheating and yet the the needle has gone as far past the red zone as it possibly can.
Just moments ago, I turned on the defrost as hot as it would go, as high is it would go. The needle jumped to that far right position, all the way back to the far left, then to the middle, to the far left and finally back to that extreme right position again. I've never seen this fluctuation before. I was told to squeeze the radiator hose, it's not over inflated or anything.
So any ideas here? Is my gauge just terrible incorrect? Is it the thermometer? Something more sinister?
(This is not the farthest the gauge has gone today. It's going even a bit further than this.)