According to a buddy who works on MBs as a hobby (he does know what he is doing) a complete radiator flush/suction should solve the temp problem. I asked him about that with my 86 560 sl and he was quick to respond. I personally havn't made the time to get it done yet, however what he said made sense.

There could be tiny metal particals floating around and therefore affecting the temperature. It's been awhile since I had a radiator flush. I don't ever remember having a vaccum done. However, he did stress the latter process. Similiar to an oil suction for oil changes.