I've got a 98 GT and have the same engine temp problem as bronco sport. I got my car new and it ran rock steady at 180-185 for a few years then all of a sudden the temp needle goes up and down like an elevator. changed the t-sat and had a flush and fill, nothing. have a water pump ready to go for the next try.

If I'm not moving I have to turn on the ac to get the fans running and sometimes it keeps the temp down, sometimes not. I also can smell it when it starts "cooking". doesn't matter what temp it is outside for this to happen.

I'm very interested to see if you find or have found the problem bronco.