On my 1991 944S2, the temperature gauge sits on the top white mark 98% of the time when the engine is warm.

I've investigated many overheating issues and finally found the sensor that feeds the temp gauge to be sending normal, correct values. In other words, the sensor says the car is running normally, but the gauge reads very hot. Maybe 3% of the time, the gauge reads normal with the needs right between the two white marks.

Has anyone dealt with this? Do I likely need a new gauge? Maybe there's a grounding issue somewhere?

thanks,
Bryan

 

Sounds like a grounding issue to me. Usually this will make your voltmeter read low and your fuel gauge read high (crap, or is it low?) as well.

 

Mine does it as well. Tap on the plastic in front of the gauge, it will likely drop into the normal range. I need to pull mine and fix it one of these days.

 

I fixed mine by pulling the sensor out of the block and then whacking the bottom of it several times against a block of wood. The cooper/wax solution that is in the sensor gets broken up; same that is inside of a thermostat. Also, make sure that the two contact blades are free of corrosion.