Hi hightech.

Does your temperature go back down again when you have finished climbing the hill? If it does, then I would not worry too much about it. I have a 190e, and mine tends to do the same thing -- the fans will kick in to high in order to provide maximum cooling for the engine as it's working harder to climb the hill, but as soon as I deaccelerate and begin to descend the hills, the coolant returns to normal and the fans slow down. We both have smaller engines (mine a 2.6, and yours a 2.8), and they need a little "extra" help in staying cool when they are put under grades.

If the engine temperature is running at that level at all times, you might need to have the cooling system checked, or to at least check the level of antifreeze in the coolant overflow tank to be sure that it's at the right level.

I'm not a real high-tech person, but I hope that this is helpful.
Best of luck to you.