Are you talking about black/brown "spots" in the radiator over-flow tank? If so, no, the new coolant will likely not "clean" those areas.....as the coolant (particularly in the reserve/reservoir tank...) is not in "constant motion" as say, oil would be, inside the ENGINE......no it will not "clean the radiator overflow bottle...
I heard one of the best solutions is to use liquid automatic dishwasher soap.....ya know the "low sudsing" stuff....heard somewhere (probably here....?) that it works......BUT, will require you taking the tank back off of the vehicle......
If it's "really" bad, probably wouldn't hurt to just find an "aftermarket" tank, and replace it though
I was considering this for my Aries, cause over the years, mine has gotten quite dingy, and actually found a small leak in it last coolant change, which I sealed up with some WaterWeld lol.....
OOOpppps...perhaps I was reading the post wrong....lol. If you are asking if the new coolant will "clean" the complete cooling system, I don't think so....I don't believe there is any "detergency" to antifreeze/coolant......though now, I _HAVE_ heard of people running various "chemicals" through their cooling systems/radiator.....
1) Prestone or other various over the counter "cooling system flush"
2) White Distilled Vinegar....yes, the same stuff we use to clean out our wash machines, coffee makers, tea pots, makes sense, it gets my coffee/tea pots clean of lime/scale/etc....probably would work pretty good in the cooling system.....?
3) Lemonade Kool-Aid, sans. sugar! LOL....supposidely the "citric acid" (Vitamin C?) in the Kool-Aid makes for a good lime/scale remover......BUT, I personally don't think I would trust this mixture in MY cooling system!
4) CLR - yes, the popular "Calcium Lime Rust" cleaner found in the Hardware/Laundry department.....I've heard of people using a quart of that, rest water, in their cooling system to "clean up".....again, I don't know if I would "trust" this......CLR seems like it's too "stout" for the radiator usage....but eh, I've heard people done it....
My favorite, seems to be #1 - the Prestone Cooling System Flush, I'd leave it in the radiator for a good week or so, drive the vehicle as normal, to and from work, errands, etc....then drain it, and refill with your preferred coolant/antifreeze %...
Though, our northern friends are nearing their cold months! I would not recommend doing this procedure into the winter months, as you could risk the engine/radiator freezing solid with the straight water/Flush solution in there........so watch the forecast!