93 Explorer, 20+ flushes in a 2 year old cooling system, coolant still brown

[Centaurious]

Your Timing cover is aluminium and its corrosion is white not brown. If it is leaking oil into the coolant it might turn the coolant brown but it would also be oily. The timing cover has a weep passage if it leaks coolant and these are to the outsides of the cover.