Citric Acid Cooling System Flush

[N41EF]

Ok, 2000 C230k, had green coolant and a leaking overflow bottle. Replaced bottle and new pressure cap, and coolant return hose that was leaking. Drained all coolant from radiator and flushed with prestone radiator super cleaner that I ran for a day of errands. Did three or four drain and fills to get the water somewhat clear, then bought the citric acid and ran that for a few hours. First drain was nasty. black and green with all kinds of sediment and crap. Been through 4 more drain and refils, and the water started to clear up, now is back to black and green nastyness. I drain the car everynight and refill with plain water, drive to work and back, then drain next night after it cools down.

1. How many drain and fills does it usually take to get back to clean water?

2. The citric acid flushed all kinds of stuff loose, anyone use it on their other cars? I'm thinking about getting another container to flush my land rover.

3. Does a M111 have a block drain? looked left side forward of the starter, found nothing. The right side is so covered up can't see anything there either.

I want to see clean water draining out before i fill with the DI water and mercedes coolant. The car does seem to run cooler, between 80 and 85 in traffic, of course the weather has cooled a bit too. Was running close to 100 in traffic with max AC on.