Anti Freeze turned brown.

Charrlie_S said
First off, I wouldn't use 50/50..

I don't know why not, and the OP is in an area where he needs freeze protection.

If you are in a position to drain and store the car for at least a couple weeks, drain the entire coolant, and let it settle, then carefully transfer the "clean" upper liquid to a different container, and let what's left settle again, until you cannot gain

I have not priced them, the old diesel truck "luberfiner" cartridges used to be really cheap for their size, you might rig a McGuiver up to filter what's left.

I think this is one, 11 bucks

http://www.fleetfilter.com/filter/wix-oil-filters/51554.html

You could probably just plug the bottom and put a funnel in the top, then "rig" it above a bucket, and slowly poor through the top hole

I don't know the condition of your water "up there," but in some areas it is almost vital to use "store bought" purified water. When I was in the Navy, my 4 years in San Diego, smart people did NOT put tap water in their systems