GTO running hot ..

[snaggeltooth]

Whenever I pull up to a drive through or at a stoplight the temp goes up very quickly and has seen HOT .. I don't think it is a sticking thermostat as it only does this at stop in gear .. As soon as I take off or put it in PARK the temp hand quickly drops back to normal ... Any ideas ...???

[PatrizioD]

This happened to me recently. Have the water pump checked; mine needed replacing. Does it seem like the temp is going up and down WAY too fast? Like faster than should be possible? I remember thinking "Water cant heat and cool that much, that fast, so its gotta be something else"
If you're under warranty, it should be free. I was, but I saw the invoice and it was $412 for the replacement (I didnt pay, gotta love warranties)