I think the Grill shutters are getting stuck in the closed position making engine run hotter than normal but not getting any error indicators on Dash. Just the top grill set not the bottom. Is there an easy way to test without service call?
I did just a tiny bit of research. It seems the shutters are supposed to go through a calibration sequence from fully open to fully closed at engine start. It might have been an F150 site and may not apply to your Explorer. But you might raise the hood and have someone else start it and watch the shutters.
Might require a dealer to service. Just a guess but independents may not have much, if any, experience with these.
I am honestly surprised we don’t hear about this more often. When I saw these grill shutters were becoming a thing I thought “here comes a mountain of headaches.” They don’t seem to malfunction as often as I thought.