I haven't had water in my radiator since last winter. I put that plug in it where it was oversized. (previous thread) Well I bought a bushing yesterday so I could use a petcock. I put in water to see if it leaked and it leaked alright. Not at the petcock but there is a pencil lead sized hole rusted in the outlet by the frame. I sanded it clean. I've got some 2 part epoxy but it's only rated at 180 degrees. That should be fine though, the water is cooler at the bottom. I've got J B Weld, or I can take it off and braze it. It didn't leak when I parked it. Amazing, it sat almost a year and I put in a couple gallons of gas choked it 4 or 5 pulls and it fired up on mag like I just drove it yesterday. Steel clutch discs wheels on the ground. If my daily driver truck doesn't get driven daily I have to work on it.
Cory, the bottom outlet is cast iron, so it will rust out. If you try to bronze the hole, you may well have to use enough heat to melt the solder elsewhere in the radiator.
The best repair is a new brass outlet. If you want to patch your old one, I would suggest making a patch of sheet brass and soft soldering this over the hole. This will not require so much heat.
Hope this helps.
Allan from down under.
I would not braze it. The heat may very well open up other solder seams as Allen pointed out ... and then your problems multiply.
Do not use plain epoxy, it will not do well with the heat.
If the outlet is basically sound, empty the radiator, turn it with the pinhole up, clean the area around the pinhole with a wire brush and run something in the pinhole itself to clean it (jewelers file - wire, etc), Scrub the area with acetone and then JB Weld (it has a much higher temp rating). The repair should last longer than the radiator.
I would try to drill the hole to a clean, rust free diameter that removes all the corrosion. Then tap the hole and install a threaded plug using some JB Weld on the threads.
I never thought about melting the solder elsewhere. I'll go with the JB Weld. I repaired a hole in a Hudson 6 cyl intake years ago and it gets hot there by where the intake and exhaust meet. I did what Royce said, it was a pretty big hole so I put about a 3/8 bolt in it with a bunch of JB Weld and it's still holding. I sure wanted to go for a little drive and not just watch it idle a few minutes.
For a temporary "shade tree" or "farmer" fix, just carve a small wooden plug and drive it in. Something like a burnt off wood match stick.
(Message edited by Ken_Todd on September 19, 2015)