Well, I am at a loss on this one. 2007 3.4l Equinox that is having issues overheating? The car is 100% fine until it warms up to normal temperatures, once it does, and the vehicle idles for more than three minutes, the temperature gage begins to climb, until it gets to the last mark before the red. The fans function as they should, and the temps still climb, but what I am truly confused about is that once it reaches the line it stays there for 30 seconds, and then almost instantly will drop back down to the normal level. The thermostat was changed in the fall, was stuck closed, but since then it has been fine up until today.

Thank you in advance everyone for your help!

 

Welcome to the forum. It sounds like you have air trapped in there. There's a bleed screw on the water pump tower that's supposed to be opened when filling the surge tank.