Overheating engine (Water Wetter sucks)

[Zoonhollis]

It was 102 degrees here in Dallas yesterday as I was driving home in my '84 300D Euro. I watched with mounting chagrin as my thermo needle climbed above 100 C. I hoped it would stay there, but after only a momentary pause, it began making its way up past 110, then on to the dreaded 120 red line. It was about at this point that I needed to use my brakes to maneuver the Arlington/Dallas rush hour traffic. But it's difficult to use brakes when your brake fluid is boiling from the intense heat in the engine compartment. It was the previous day that I drained my radiator (save for about 15% antifreeze/water solution), and added Red Line Water Wetter. I'm convinced this stuff is really just strawberry-flavored Kool-Aid.

Actually, the point of all this is a question: should my aux fan have been running, or does it run only when the A/C is on(which it wasn't)? After my poor Benz cooled off, I drove it around to warm it up and see if the aux fan would kick in. It never did, until I cranked on the A/C. Is this normal? I know that 120 degrees centigrade is NOT normal! AAARRGGGHH!!!

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Matt
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'84 300D Euro