so i had bent/split one of my cooler lines and i wanted to know if i could use copper tubing instead of steel? reason is that i have ready access to the same size copper tubing and the tools needed to bend it to shape.

almost finished my engine, will post pics of final painted product.

 

I think copper would work for a while, and maybe a long while. The reported issue with copper line in an automotive application is supposed to be that the constant vibration will cause the lines to fatigue and break. I have heard reports that this is untrue, but I don't know for sure.

I do know that the single flare tools commonly used on copper line WILL NOT work on your stock trany line ports without buying new adapters, and you will still need to use i/f to std. flare adapters at the radiator.

This being the case, I THINK you would be better off buying 5/16 steel lines (about $8 each or less), a $12 Harbor Freight bender, and a cheap or borrowed inverted flare tool and go at it.

5/16 line is easy to work with, and can be bent by hand with some patience. (get the sticks, not the roll though)