I have a 2014 traverse and for a period of time the temperature has been going over 210. It fluctuates between 215-230. It only does it when going slow or idling. I have checked the coolant and it is to the fill line. I’m having the whole coolant changed on Friday. I have read that maybe there is air in the system. But I am also wondering if it could be something more. The fan stays on after turning it off and while running it gets so loud like I have never heard it before. Please any recommendations would be greatly appreciated. I am trying to avoid something very expensive happening.