1987 260E Overheating

I have an 1987 260E, 143,000 miles. Since it has gotten warmer, the engine continues to heat up above the normal 80C while in traffic with AC running, once on the open road, temp seems to return to near normal. Aux fan is working, full of coolant, new radiator several months ago due to an accident. My thoughts were the thermostat or the fan clutch. Any suggestions, on how to determine where to go from here.

The best advice is to replace the thermostat at once. It can be done at home in about 10 min!! You can get one at your local parts store. Be sure to overfill the coolant untill no more will go in. If you don't you could get an air pocket and overheat the engine.

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Benzmac:
ASE CERTIFIED MASTER AUTO TECHNICIAN
LEAD TECHNICIAN FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM

I have replaced the thermostat as suggested, it seems to have helped, temp has not gone above 100 deg, have not driven in hotter than 75 deg outside temp. However, driving on the highway, outside temp 70 deg, temp runs just above the 80 deg mark. At stop lights with AC on, temp goes to 100 deg mark. Is this type of temp variation normal? Once car begins moving, RPM increase, temp moves back down.

Any further suggestions, would be appreciated.

This is an excellent site with great info.

Normal operating temp. Nothing to worry about.

IF it does go above 100, I would replace the fan clutch. IF it is faulty it will make a huge difference!!

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Benzmac:
ASE CERTIFIED MASTER AUTO TECHNICIAN
LEAD TECHNICIAN FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM

Thanks for the information, the fan seems very easy to turn when the engine is stopped. Unlike my 83 380 SEC where the fan is somewat tight. I know the fans are not the same, but is this a further indication that the fan clutch is bad. Also, any idea on the approx cost.

Thanks again for the input.