Fixing a Brass radiator?

[Birch Hill Farm]

I have an old international 444 tractor with a brass radiator. It is leaking along 3" of the seam between the top and bottom parts of the reservoir tank. There is no direct fit replacement radiator available for this tractor so, the only option is to fix this one or modify a radiator from a close model to the 444. I was thinking of cleaning up the seam and soldering it with regular plumbing solder or use some of the sticks of silver solder that we use in A/C systems. Will this work? what kind of solder should I use?
here is the seam in question:

 

[Gary Fowler]

I would remove the top clean it all up and resolder the whole thing rather than patch it. The problem with trying to patch a spot is that you have to melt the other solder to do it and then if it is dirty the melted spots will then leak. Best to just heat the whole thing up, pull the top, clean it by heating and brushing to remove all the old solder ( a little muriatic acid might be needed to remove any old scale) After it is cleaned good, just set it back on and use any available solder. 50/50 Tin/Lead solder is getting hard to find but any grade has a working temp higher than your radiator will ever see and they all flow about the same.p You will need a torch to do this as a soldering gun wont put out the heat needed. Just play the torch equally to both sides of the seam and add the solder to flow in just like sweating copper fittings.
If the core is good, you will be lucky. My JD 332 had a leak and the core was bad, had to replace the whole thing for nearly $400 and this is a lawnmower.
Oh, while you have the top off, check the core tubes and clean them if they are dirty. Most radiator shops I have seen just use a couple of hack saw blades tacked together to be long enough and then grind off the saw edges. Some have double stacked thickness hack saw blades due to the width of the core tubes the length seems to be perfect match for the hack saw blade. Just be carefull not to puncture the side walls of the core. Muriatic acid bath would clean them also if you have something large enough to put the radiator in.
Alternately, just take it to a radiator shop and have them clean it and repair the seams.

 

[Birch Hill Farm]

Thanks for the reply. Good information and it fully answered my question.

 

[Soundguy]

yep. remove it.. cleani up both surfaces.. resolder with silver plumbing solder and use lots of flux...

btdt on antique rads and tanks...

 

[crazyal]

Have you looked around for a radiator repair shop? They should be able to get a new core for it and just reuse the tanks. In our world of throw away places that will repair radiators is dwindling in number.

 

[yomax4]

If you do repair it, Look for a low temp silver bearing solder like Harris Stay-Brite ( 4% silver ) or Stay-Brite 8 ( 8% silver ) The cool thing about these products is that they both go liquid at between 480 and 540 degrees. They when you re-heat to add another piece you will notice that the re-melt is a couple hunderd degrees higher. You can add parts and pieces without worry of the whole thing melting apart. As stated above. Lots of pre-cleaning and lots of liquid flux and lots of water wash when done. Fun Stuff... Side Note. These solders have a long plastic range, Meaning they stay liquid for a few seconds before they solidify. Solder a couple copper fittings together 1st to get the hang of it.

 

[Raspy]

I was thinking of cleaning up the seam and soldering it with regular plumbing solder or use some of the sticks of silver solder that we use in A/C systems. Will this work? what kind of solder should I use?

Silver solder used in AC systems is commonly silfloss or 15% silver. This will not work on your radiator! It melts at a much higher temperature (about 1450 degrees) than the solder used on your radiator.

A good choice is the original solder material that was used. It is simply soft solder or lead solder. You can get this a roofing supply companies for gutter work.

A better choice might be Silvabrite 100 which is a stronger lead-free material. it is a direct replacement for lead solder and was put on the market to replace lead solder in domestic water piping. It's readily available and is easy to work with. It is also a stronger metal, so the tank might not split as easily. It is only better in this case because it is stronger, not because it is lead-free. It is a bit harder to fill voids with than soft lead solder because it is less viscous when liquid. This makes it harder to fix radiators with loose fitting pans. You can't stack it as easily.

Lead solder is good because it melts at the same temp as the rest of the solder in your radiator instead of higher. Higher requires careful heat control so you don't melt the solder holding the tube assembly into the lower pan.

Don't try to fix any cracks with soft solders by just soldering over them. It won't hold the pressure for long.

There's more to the story than simply saying "Silver". There's a huge difference on the material strength and the melting temperature. Even Silvabrite has .4%. You need solder for water piping, either soft lead or lead-free. Lead-free has trace amounts of silver. But is not silver solder, per se.

A good water base flux like C-Flux works very well. Lots of flux applied with an acid brush as you go, lots of wire brushing with flux on the surface. Careful heating and dipping the solder in the flux before applying it to the surface will help. But heat control is the most important. Just enough to melt the solder in the area you are working and make it alloy with the soft solder already there. It's a skill you can work on and should before doing your radiator.