I thought I remember reading a post here in the past week or so that basically said that if you are doing highway speeds the fans are not the things cooling the engine, that it is mostly the air at speed cooling the radiator.
My car also runs at 100 when stopped in traffic for a while with the a/c on.
My guess is that your thermostat is sticking and needs to be inspected at least.
You aren't hearing any horrible noises when the cars running, I think an old toyota of mine made a crazy noise when the water pump went.
I don't personally know how you tell if you have an air pocket in your cooling system but if someone else on this forum knows how to diagnos and correct that I would be interested to hear the explaination.
1985 190e 2.3