During driving sometimes,my temp gauge will drop from middle of hot and cold to cold.I parked the car once and found that the radiator cooled off while the car was running.Turned motor off 5 minutes and started up.Temp came back okay.It does this once in a while.Any clues as to the problem?Anyone been here?

 

Probably corrosion on the temp sensor connection. Find the sensor on the engine near the driver end of the front cylinder head. It is a one blade connector with a square black boot. Check for corrosion on this terminal.