I'm not sure if I want to tackle this, but I have a very small leak coming from the filler neck. I was going to sand it, flux it, and weld it.. thu it's been a while since I've have to fix a radiator.. Is there a newer/modern, better method theses days.??
By weld, I actually think you mean, solder, but anyway, without completely removing the neck and assuming the plating on the neck is nice and you want to keep it that way, after sanding the radiator top near the leak down to bare brass, you might try just a drop or two of flux or mild acid to clean the area near the leak. Then try to apply some solder, using as little and low heat as possible. Too much heat and you can forget the plating on the neck. I may be wrong, but originally, I think they were sweat soldered to avoid as much direct heat on the neck as possible.
Did you read the other thread about fixing leak?
I've been looking for the other Thread, not much luck .. but the low heat is where I'm not clear. I know enough, that I have to heat it to melt the solder. but I didn't know too much will effect plating.. though I should be OK then since i'm using brass...
RVB, excessive heat will cause the plating to turn bluish hues. Sometimes, if the bluing isn't too bad, it can be polished off. If you need to see what I'm talking about, find a motorcycle that's driven daily and not maintained daily. Chances are the exhaust pipe near the head or block will be discolored. When soldering, you could try a moist towel or rag wrapped around the neck away from the heat to act as a 'heat sink'.
Ifn you're not proficient with a torch, use a big soldering iron.
"using brass"? Does that mean brass rod and acetylene? If so, that's WAY too much heat. You'll be burning holes in the neck, or the radiator, or both. I agree with Ken. Big soldering iron, not a little soldering gun.
Here's the other recent thread on radiator repair: http://www.mtfca.com/discus/messages/506218/518895.html?1426470686
If you get it hot enough to melt a brass filler rod, I bet every solder joint on the upper tank will come loose.
You need to practice on some junk before you tackle the radiator neck. It seems to me you stand a good chance of making a real mess unless you hone your skills with a little practice.
For me a propane torch using a small tip works pretty well when repairing a T radiator. It produces low heat that's just right repairing thin material.
I replaced the radiator neck on an older flat tube radiator for my 21 Touring rebuild and it worked out well. I used silver lead solder and liquid flux that produced a smooth joint.
I couldn't find a shop in the area that would do it so I did it myself.
The local shops seem to be afraid to work on older radiators. I have to say 'it ain't rocket science'. Technique and surface preparation is easy enough for anybody to learn.