[Enjin]

I bought this car and noticed that the radiator overflow tank was very dingy with brown stuff all on the bottom.

I thought it couldn't be good, so I drained the radiator fluid. very brown. I open up the radiator cap to see brown in the radiator. so I flush it with about 10 gallons of water into the same container. the brown from the radiator disappears. I take off the hoses, to see brown residue in the top radiator port or whatever.

is this indicative of anything? best way to fix this is to just hook everything back up and run fresh water through it 5-10 times?