Acura Repair: Intermittent Overheating, radiator fluid, radiator fan

Question
My son's '91 Legend will run fine for a while, then the temperature climbs fairly rapidly and most often then drops down again quickly even if he continues to drive it. . .There have be a couple of occasions when the temp didn't drop right away on its own and he had to pull over for 5-10 minutes before it dropped again. . .We thought thermostat and replaced it, but the problem persists. . .Any thoughts?

Answer
Hi Bern,

This issue could be due to a bad temperature sensor, do you feel a change in the car's performance if the temp goes up? Also what is the outside temp of where you live? Does the radiator fan turn on after 2 minutes of running the car? Do you see any radiator fluid leaking? Check the heater core if the car has one, the gasket on that heater core does tend to fail after so many years, there could also be a crack in the radiator. To check for leaks you can use a dye pour it into the radiator and run it for a few days then use a UV light to check for leaks. The dye is a special automotive dye.

Thanks,
Daniel