I have a 2017 f150 3.5L ecoboost with 26,000 miles on it. Recently I've noticed that when the truck is making about half boost pulling a hill and the boost drops at the top of the hill the temperature numbers start showing up on my dash, like it's getting warm. It never happens while while the truck is building boost, always shows up about 8-10 seconds or so after boost is gone, ie cresting a hill with cruise control on. I can understand getting warmer while building boost, but warmer after boost is gone makes no sense. Yesterday I had my cruise set at 75mph, 10th gear, and about 10 psi boost. I hit cancel on the cruise control and the numbers pop up, if I hit resume on the cruise (still on the hill) the numbers will go away all the way to the top of the hill, once boost is gone, numbers will pop back up. Most of the time I see 230 or 232, but have seen as high as 236. Talked to ford and they say, that it could be that I need to add coolant till it is just above max. I'm currently just slightly over min. Does that make any sense. I was thinking it had something to do with the grill shutters closing at the wrong time? Here's a couple of videos if the links work. Give me some ideas, cause ford is scratching their heads a bit.

https://drive.google.com/file/d/1-yE...BHPdOwlBt/view

https://drive.google.com/file/d/171-...wxVidfKhb/view

https://drive.google.com/file/d/1xBR...X25vaiOSP/view