[olddog]

I'm no machinest, but I did stay in a holiday inn last month.

It would seem to me that if they drilled into a water jacket, it could be fixed. Tap the hole almost to the bottom, so that the threads go to the bottom but are tapering. Then use something like a set screw. The tapering threads should act similar to a pipe thread and the set screw should tighten up at the bottom. A good sealer on the threads should then give you that extra layer of protection.

Maybe this will give someone else a better idea.