well i use to clean my cars radiator after every 3 months.
- drain all water.
- re fill radiator vid clean water and start your engine for 2 or 3 min.
- again drain and rinse radiator 2 or 3 times.
- add 1 n half can of coolant, than fill water.
- half in the overflow bottle.
- go to service station and ask them to clean radiator fence vid pressure,,but not to0 close.
- and clean ac fence underneath the dashboard.
thats what i do every 3 months,,,, my water never gets rusted,,, but it changes it color bit. but not rust or brown.