As for the electrolysis, I do have a
zinc anode installed.
You are not suppose to ground the radiator. I've read the instructions thoroughly from Ron Davis and part of my problem was the fact that it was touching a ground source - the frame! When I finally finished installing it after repairs, I took a continuity tester to it and there was NO contact to ground.
It's just that the second leak was likely either too thin to stay repaired as you were alluding to, or my original electrolysis problem affected an adjacent tube.
After thinking about this some more, I'm inclined to just remove the entire tube and seal it like you suggested. There's no point in putting heat to it again and possibly fatiguing the tank any more.
Thanks for your reply.