Will running only water in the summer hurt anything?

Reason I ask is cuz the car was purchased with rust built up in the raditor and the coolant was brown. After draining and flush many times its has cleared up but the radiator is still rusty inside.

also, Any tips for removing the rust build-up?

 

replace the radiator and use antifreeze, no exceptions

 

Water only doesn't hurt anything.

Buy a chemical flushing agent and flush with that.

 

Straight water has a lower boiling point than a water/coolant mix, and doesn't have any of the anti-corrosion agents that are in coolant.

 

Straight water does have a lower boiling point than a water/anitfreeze mix, but it also has better cooling properties. The 15 to 16 psi that the cooling system is pressurized to will actaully provide the raised boiling point necessary. If you want to run only water, then you should add something like Prestone anti-rust into the system. This will prevent the corrosion issues.

I live in Phoenix, Arizona where we don't have much need for anti-freeze protection in the winter, so I have ben running this setup for years without issue.

 

i run straight water just because i went through 3 cases of antifreeze from leaking head gaskets, head swap, intake swap, motor rebuilds, etc.. just didnt see the need for more money to enter the pot since the coldest it gets in hawaii is maybe 30's with windchill.. and i run just fine at 155 on cool nights and 165 on the highway.. with 175 in traffic on a high 80* day..