Cooling system keeps filling up with a thick brown rust?

Im having a cooling system issue, my cooling system keeps filling up with a thick brown rust and I mean thick you can spoon it like mud ive had to replace my rad, waterpump, serpenten belt, my water pump locked up due to this stuff ive had it flushed 12 times its ok for 1 wk after flush then back to the mud again I use good antifreeze, rust prevent and lube and have even used distilled water to try to help it only has 63000 miles on it uses no oil, comp ok, small loose of water. Ive even tried using a hotter thermostat and a cooler one any help will be appreciated since im out of ideas thank you