Radiator Repair: Soldering 'Contaminated' Cast Iron Neck
 

So far I've done a lot of work on a 1940 honeycomb radiator for my late '30 CCPU. This is my first radiator repair that I've taken to a multiple component disassembly level. One of the very last steps is to fix a leak between the upper tank and the cast iron inlet neck.

(See photo) When I removed the inlet neck there was rust at the seam, so it was easy to spot where the leak was. It actually looked like they didn't put enough solder on the joint! Cleaning the tank was fairly simple and only a smooth coat of solder was left when I finished. The iron inlet neck was another story.

After I removed the old solder and the rusty crud, I noticed that the inlet neck mating surface was discolored. My guess is it's from embedded rust and/or old chemicals.

I wire brushed it and cleaned it with MEK, but the discoloration remained. I attempted to tin the surface and the solder did stick, but it didn't want to flow. I'm guessing something is still on there.

Any ideas for cleaning the cast iron neck? Sand blast? Acid?

But wait, there's more! The tanks mating surface for the inlet neck has a wave in it. Not major, but enough of a gap to keep the solder from sealing it
up. If push comes to shove, before I solder it I'll put some small screws into it to close the seam gap...but that's my 'last-ditch bail-out' move. Any better ideas?

Re: Radiator Repair: Soldering 'Contaminated' Cast Iron Neck
 

1930-pickup
sand blast and then clean with muretic acid then tin it. In my dads shop we would use brass exploding rivets if push comes to shove. Not sure now where you can get them.
Ed

Re: Radiator Repair: Soldering 'Contaminated' Cast Iron Neck
 

You need to flux the joint for solder to stick, get the flux that is compatible with the solder you are using ! You should be able to fill the gap by multiple attempts :-)

Re: Radiator Repair: Soldering 'Contaminated' Cast Iron Neck
 

Ed. Would you care to explain what a "brass exploding rivet" is. Never heard of it. Jack

Re: Radiator Repair: Soldering 'Contaminated' Cast Iron Neck
 

Watch this youtube video. https://www.youtube.com/watch?v=qUEbePVyS3c

Bob

Re: Radiator Repair: Soldering 'Contaminated' Cast Iron Neck
 

Sandblast the neck. Flux and tin the surface. Do the same on the tank. Then put the neck in place and use a soft flame (carburizing) on the cast neck to take the heat. when the solder starts to flow add in your solder and make the joint.
The tricky part will be getting the heat into the neck without over heating it and burning off the solder.
John Poole

Re: Radiator Repair: Soldering 'Contaminated' Cast Iron Neck
 

Thanks Ed :)

Re: Radiator Repair: Soldering 'Contaminated' Cast Iron Neck
 

As a last resort, are you up to fabricating a brass replacement or even using the old piece as a pattern and having a new brass one cast. I'm sure you could sell a few if you made extra.

Re: Radiator Repair: Soldering 'Contaminated' Cast Iron Neck
 

Only if you can identify the manufacturer of this radiator, and the quantity still out there today, and how many of those need an inlet neck.

Re: Radiator Repair: Soldering 'Contaminated' Cast Iron Neck
 

Is the neck different from other radiators? If so, is it possible to make one that will do both? Just an idea. The final decision is yours.

Re: Radiator Repair: Soldering 'Contaminated' Cast Iron Neck
 

High tin content solder will flow & stick a lot better in the spaces that' aren't close enough for 50/50%.