You just poor alum-a-seal inside of the radiator. If the hole is stripped, you best bet maybe JB Weld. Only thing is, everything will have to be clean and dry though. Also the original JB Weld is a lot better than the 5 min stuff, but it has to sit over night, and will not make 2 parts stick together untill it is dry and hard, so you have to prop up what ever you want to put together. If I was doing it, first after everything was clean, and no anti freeze or water could leak out, I would remove the plug. As long as the plug stays in place, and doesnt fall out of the hole in the rad., your good. I would mix the JBWeld, and put it anywhere that it will make contact with the hole in the rad., Then screw it back in, and leave it until the next day. As long as the threads are covered in JBweld, and you can see it all the way around the fitting once it is screwed back in place, that should work. I have sealed a leak in an engine block with JBWeld before that was leaking antifreeze, and it held for several years, untill my mom traded in Her car. You will want to pick up some lacker thinner when you get the JBWeld. This will cut the JBWeld and let you clean up your mess. This stuff get all over when your working with it. Just follow the directions on the package. Its a 50-50 mix of the 2 tubes in the package. It wont take a lot. Mix it on something like an old piece of cardboard, and I use a popsycle stick to mix it with. Just remember, once this is done, there is no undoing it. It will be permanent.
