Cleaned out radiator with Limeaway +++ Flushed trans
 

My 85 300SD- Pulled rad, Mixed 1/2 BOTTLE OF LIMEAWAY and water filled rad up to to of hose nipples, let sit overnight drain out, back flush throughly, , also cleaned out trans cooler and flushed trans - one hose into bucket, fill as pumped out while slowly shifting through gears, used 2 gallons ATF - requires 2 people, but I have done it alone many times on all my cars -chevy-ford-dodge-volvo for years, quick and easy. Replaced AF with Zerex G05, Temp dropped 10-15 degrees! To 82. This is on a all copper radiator.

Where did you get an all copper radiator made for a 300SD?

ditto
if aluminum like every other I've seen, be prepared to replace it soon

I bought a copper & brass one a couple of years ago from somebody on the West coast -- Seattle, Portland ..... I thought it was Radiators.com, but I just went there & the site looked odd.

It was maybe $160 ..... correct fit, no problems.

I used to flush neglected cooling systems with diluted muriatic acid. You'd be surprised how much crud that stuff loosens. I had one car that had coolant that looked like mud (not my doing). Anyway after running that car for about half an hour hot with the acid, I drained and flushed out that crap. It was spotless after that. The radiator insides shined bright as well.
Neglected coolings systems don't worry me one bit. I manage to get good deals on those.;)

http://www.csfimports.com/home.asp

This outfit makes copper rads for benzes for a good price. One came with my 84D. Only thing I don't like about them is no drain cock.

um, that would be a sale ender for me...