Mercedes Benz repair: 1989 Mercedes 300se - coolant temp, coolant temp, temp guage

Question
I just bought a 1989 300se. On the highway coolant temp runs a little over 80. When in stop and go traffic it heats up to over 100 within ten mins. I drained radiator and took out thermostat to flush and it looks new and I see no corrosion whatsoever. (Average daily temp now = 85F). Radiator hoses both hot about the same time after starting so I believe its OK. Is this just normal for this car?

Answer
normal operating temp is 80-100 degreesbut with an erratic temp guage in traffic it is a bad fan clutchone way to check is getting up to normal operating temp and put a piece of cardboard thicker piece and if you can slow down the fan it is shot another way to check witha friend is get up to normal temp and have him shut off car fan should only make about 2-3 revs and stop. check for white smoke out of tailpipe of course and external leaks