I did it on my SDL last summer, dropped quite a bit. 4-7C easily.

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I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

I also wasted plenty of time before finally replacing the radiator (due to a broken neck) and actually solving the problem.

Replacing the rad in mine dropped approx. 20C on average. And thats with a generic-brand radiator, not even a Behr one. The fin pattern is totally different.

I had no idea running pure tap water was a bad idea, I've had that in my system for about two weeks. I was meaning to change it out for 50/50 water/alum-safe antifreeze but just didn't get around to it. I guess I'll do it first thing tomorrow.

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1983 Mercedes-Benz 240D
Automatic, A/C, Power Sunroof, Power Right Side Mirror
231K Miles FOR SALE MAKE OFFER

60/40 is what should be used.

Original radiator! Well thats your problem, lucky they are cheap for those cars! Well compared to an SDL radiator.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

The fan has nothing to do with cooling at highway speed.
If your sure the thermostat is operating correctly( I have seen bad ones right out of the box) , your belts aren't slipping,your lower radiator hose isn't being sucked together(rare), then it's probably the radiator.