J-B weld for some reason doesn't quite get it. I used that tough steel crap in the clear plastic tube. Keep patch area clean, anti-freeze dry, and use 100 grit sand paper or so to lightly burnish repair area. Pinch off a couple inches of the compound in the tube and knead with the hardener thats rolled inside. The stuff stinks a bit and will be dark gray. You have about 5 mins. to use it. Use usual tricks " use brake cleaner or acetone," lightly to etch... a turkey baster to lower anti-freeze in rad. etc. I have used three tubes of the crap, and have driven 5k miles. It's not a permenant fix, but if you do it right it will work pretty well for a while...mines held almost 6 months... good luck