How to know if problem is thermostat, temp gauge or sensor or something else?
I have a 2004 Chevy Impala: the temperature gauge shot way up to the red,
& even past it, & is staying there, even when the car sits overnight. The
radiator is full, and I added the proper coolant to the reservoir. The car is not
overheating -- in fact, everything seems to be fine (to me as a non-
mechanically-inclined person anyway). So now what? How do I know if it's
the thermostat, temperature gauge, radiator, or something else?