Is that just a grand prix thing, cause I've owned a bunch of cars and trucks and done a bunch of racing and never had this happen with any of them. If they ever go over the middle then it was on the initial warm up and then they would get right back in the middle and then never move again. All my vehicles have been the same, it heats up to the middle(which the middle line indicates the optimum running temp) and the vehicle maintains that temperature. And every time I changed thermostats to a lower temp one, my vehicle would maintain that temp. It never mattered if it was cold or hot as $hit out, they always were able to maintain the right temp. So I assume there has got to be a small problem somewhere.
And on the old motor she had the fluid changed and the shop bled all the air, and also her uncle thought the same thing so he tried bleeding air and got nothing. The problem never went away no matter what they did.
