I think I've read all the threads on overheating m103s on this and other forums.

I've just been driving around Southern Europe. 1990 Mb 300E. Temperature is stable between 80-90 most of the time. Had a few occasions of outside temperature of between 95-100 F. Idling in that temperature brings the engine all the way up towards the red line. I had to stop at the side of the road on the highway once to let it cool down. Next time I put the heating on max and I just about made it through a 2 hrs jam on the German autobahn. Again in 95F.

My viscous fan is pretty good I think. At least I can hear it engaging and roaring. But it doesn't cool enough when idling I guess.

I have automatic climate (button type) but there is no gas in the system. Two aux cooling fans in front of the radiator.

So heres the funny thing about my aux fan - low speed fan comes on with the ignition if outside temperature is more than 68F even with cold engine. it stops after a while but comes on again like it should if the engine gets very hot. But after an hour or two maybe, of driving - they are completely dead. Even when the engine was close to boiling they didn't start. Tried to tap the center with rubber hammer, tried to disengage the various sensor but could not trigger them in any way. Then when the engine cools all the way down, they start with the ignition again.

I have replaced the coolant temp sensor (4 pin) the one all the way in the back of the engine block. Replaced (aux fan high speed?) relay behind the fuse box, replaced ac pressure/temp sensor(?) the one down below the left head light. All fuses are good. Reservoire cap seems to be good. I guess my thermostat is good as it is only in extreme conditions overheating occurs.

I have a hard time diagnosing this in back here in Norway as it never gets that hot. Any clues guys?