Last year, when my coolant overflow tank started leaking, I got a sort of white chalky, milky film all over everything, and it wouldn't flush cleanly, unless I scrubbed it. I mean, regular water pressure alone wasn't enough to wash it off.
It dried, and then in order to remove it, I can take a wash cloth and just plain water, and rub it off, and it will come off.
A couple of months ago, when I drained my radiator, ran some water from the outside hose through the upper radiator hose (a lame attempt to flush the system), and some of the coolant dripped on engine parts, it too left this white residue, which, although easily cleaned by the method I described above, still made me question just what I have running through my coolant system. I drained all I could, replaced the coolant recovery tank, then added some Water Wetter and Orange antifreeze, but I am considering to do a Citric acid flush when it comes Spring time.
I did one years ago, to my 1979 240D, purchasing the citric acid crystals from the Mercedes Benz dealer, but with all of the posts about citric acid eating away at the water pump, causing leaks, etc., I'm kind of worried about using it, and perhaps my Orange coolant and Water Wetter is enough.
What do you all think - is the risk of things going wrong worth flushing with the Citric acid crystals? By the way, when I purchased this 1983 300D 7 years ago, I installed a brand new radiator, as it got a little too hot for my liking, and the car had set for ~ 2 years before I purchased it. I have never had a problem overheating, and don't really want to mess up a good thing by doing the Citric acid flush. What do you all think?

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1983 300D (Hans)