MTFCA Forum

"Solder will go where there is flux."

Before I attempt repair of the dripping seam, I have some questions. What is the opposite of flux? Is there something I can apply where I don't want the solder to go? Or should I mask where I don't want solder, apply flux, and pull the tape before soldering?

Is there a particular type of flux that would be best for this?

Ditto solder: Is there a particular type that would be strongest and seal best?

How shall I clean the seam before soldering?

search internet for "heat sink putty"...you'll find several

as far as solder goes, they will all have the same general structural qualities relative to the job you wish to do.

what you should be asking is: do I want a wide temperature range plastic state, or do I want a very narrow plastic state?"

to that, I would say that you are wanting to flow and fix a leak without heating the whole thing up and it falling apart...for that I'd use a eutectic solder (63/37) and RMA paste flux so that it flows almost instantly with little detectable plastic state. If you were building an entire radiator, you'd want to use a 60/40 lead solder which has a very wide heat range for plastic state.

really, most important is clean brass and RMA flux ONLY where you want it to flow.

Technique is important in that you want a solder bridge between the tip and the part so that heat will conduct out of the iron and into the work. Laying a dry/hot iron on work will not heat your work-space.

200W iron, with clean and bright tip, tinned with your solder and routinely wiped clean on a damp sponge and immediately retinned...you always want a bright silver tip/face on the iron to work with...that is your ideal tool.

DO NOT USE PLUMBING FLUX OR ACID CORE SOLDER. Again, RMA (rosin, mildly activated) flux is all you want to use. RMA cored 63/37 solder and RMA paste flux is what I keep in stock. You will not find it at ACE or Home Depot...MSC or similar supply houses will be your best bet.

Various techniques are discussed in this link related to brass instruments https://www.trumpetherald.com/forum/vie ... ?p=1160489
Since you are working with metals solder (tin+lead) and brass (copper+zinc) removing one it with an acid solution likely will harm the others.
Looking at the piece is would not try a brushing method using some of he above (steel wool, old cotton sock) but using desoldering tape that is used to remove components from a circuit board. It acts like s sponge and will get most of it off.
If you have a leak, the heat applied when removing the excess solder may seal it up. I wouldn't try to fix it until the excess was removed and you test for leaks again. --
--The sell a special high temperature tape to protect areas from getting soldered. Now experience with these --
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You also need to consider using the correct alloy of solder
https://info.mayeralloys.com/blog/3-thi ... -radiators

Kapton tape is for work on IC boards using a needle sized iron on components which typically are around 1/32" (and smaller)...I've got plenty of experience with it. It will provide no heat sink protection against a long dwell of a 200W iron and a 1/2" wide tip. The insulation it provides is electrical...not heat.

It has its place...just nowhere I can see on radiator repairs.

Has anybody tried to use a non-heat type of fix on thin seams like brass radiators have? It will seem like craziness, ignorance or just won’t work thinking that will come to a conclusion that it wouldn’t.
New types of glues or epoxy might work to seal a seam like your radiator has. With the improvements in types of glue that comes in clear or a blended color and not requiring heat to get a good seal might work and be hardly noticeable.
Of course some will roll their eyes and shake their head but it might work since a repair like yours wouldn’t take a lot of heat even with a small tip soldering iron.

Just food for thought but sealers and glues have really improved the last few years and lots of older folks haven’t kept up with the times or think it’s completely wrong to use on a T.
Just my opinion and others will have theirs. If that radiator were mine I would try it since T radiators are not pressurized as much as modern or newer radiators are.

Kapton tape is for work on IC boards using a needle sized iron on components which typically are around 1/32" (and smaller)...I've got plenty of experience with it. It will provide no heat sink protection against a long dwell of a 200W iron and a 1/2" wide tip. The insulation it provides is primarily electrical...think ESD...not reallyfor heat (though it can WITHSTAND heat from soldering, it still is not a heat sink).

It has its place...just nowhere I can see on radiator repairs.

Here's a tip: build yourself a rheostat controlled plug to control the iron's temperature. This keeps you from burning the tip with excess heat at the tip.

Mine is a handi-box, light dimmer, and a duplex plug. I use it for large soldering jobs and my oil-pan heater on my jeep

If you're an electrical-type guy and have a Variac, use that instead.

Suggest you watch this video to see Gery Berg build one from scratch. Watching what he fluxes and solders
https://www.youtube.com/watch?v=wbQMbpHEiAo --
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More by Berg on a rebuild
Part 1 https://www.youtube.com/watch?v=O4Z58zC-l1Q
Part 2 https://www.youtube.com/watch?v=aehHwPlaxhU

If your leaking seam is what I perceive to be up at the top of the radiator, I would carefully "finger" on a bead of this clear stuff called "Seal All"...it really works. It'll even stealthily seal your bottom seam, in fact I have that on the side of my Torpedo now, it's held up all season long. Worth a quick try.

Seal-all looks pretty good. There is a you tube video that tells about it.

This would be a good product to use if you want to be sure to never be able to repair this brass radiator properly ever again

being that there is a correct and relatively simple way to repair this radiator, I am simply amazed at the creativity that goes into discovering improper or deleterious ways to accomplish the same thing.

how someone wishes to maintain their own vehicle is none of my business, but if someone is asking for good advice, then I believe that when bad advice is given, it is fair game to point it out.

hot enough to flow the solder, and the solder will tell you when it's hot enough

eutectic solder flows/solidifies at 183C...others will turn plastic at one temperature and flow at another...all hotter than eutectic solder

a 200W iron will heat far past the temp you need, to the point of eventually burning off its plating (if plated), thus my recommendation to throttle that thing with a rheostat. Keeping the tip clean, bright, and tinned, using a damp sponge and reapplication of solder is paramount.

if you fool around with a thermometer, the whole process will easily get away from you.

if the solder is sticking to the work, and "blobs" of solder are forming, you have a cold joint, and either the iron is too cold, there is no solder "bridge" between the tip and the joint, or you have moved to a new spot too quickly and too far away from the last place the solder was molten. When the solder flows TOWARD your iron by itself, you're where you want to be regarding cleanliness, flux, and temperature.

again...200W iron (AmericanBeauty, EG)

if you're hoping to do this with a small iron or soldering "gun" like used for model railroading or radio repair, don't even start. Simply relax in the shade, have a beer and thank your lucky stars you didn't make things worse.

In addition to Scott's excellent advice, I'm thinking this discussion begs for the experience of a very skilled radiator repairman. In this case, I'm wondering how it would be possible to clean that folded interior joint to make the repair successful ?!?

'Flowing the solder' means the base metal is heated sufficiently to liquify the solder, not just a hot tip melting the solder on a cold substrate. Everyone probably knows this, but a 'cold' solder plaster over a cracked seam will appear fine and not leak until the solder fatigues and the crack opens. For this to work the gap between the brass parts needs to be clean and closed and the brass heated sufficiently for capillary action to draw molten solder into the space.

And as others have cautioned, don't plaster any goop or sealant on the radiator, you will never get solder to properly work after you contaminate the brass. If you are purchasing a soldering 'iron', I would recommend going even larger than 200W (eg., 800W with variac), a combination that has served me well over the decades. YMMV, good luck.

inside that seam is solder bonded to both parts. Generally, you can expect that the crud will float out of the molten solder when fluxed and heated due to the solder's density

where you get into trouble is when bare brass (or whatever substrate) is contaminated with silicone or other contaminants and the brass simply will NOT tin with the solder. Right now, you have solder tinned to everything and are trying to reflow it to bond back to each other

Wow! The soldering iron prices say this job will wait a few paydays.
Fortunately it's not a major leak.

Good tools don't cost, they pay...

(yes, they are spendy...maybe find someone to lend one?)

Steve Jelf wrote: ↑

Tue Sep 27, 2022 11:00 am

Wow! The soldering iron prices say this job will wait a few paydays.
Fortunately it's not a major leak.

Steve,

Check out eBay or maybe Craigslist for an old American Beauty electric soldering iron. New ones are very expensive, but I've found old ones for maybe $25 in junk shops.

Here's 300W version. Not $25, but way less than new... https://www.ebay.com/itm/354226250404?e ... R9bXw_rvYA

Jerry, eBay is a very good idea

to add to that, I'll say that the tip should be a two-sided chisel-tip, not the diamond pointed one...you will get FAR more heat transfer with the broad side of the tip, and additionally, a new tip will have good tinning and will make for the best job. Buying an old iron is fine but using an old tip is like buying an old milling machine and using dull cutters. Nothing wrong with the old machine, but everything is wrong with using dull cutters.

Be careful with used irons, don’t give much for them sight unseen. I had one few years back that was fine as long as cold. But when hot it would shock the blank out of you when you stuck the solder to it.
It ended up in scrap copper bucket.

Dan, it's not nice to laugh at someone's misfortune, but I'm still snorting over that one!

please forgive me!!!

Scott: Best part was when I Wife helped me do some soldering and she feed the solder to the iron.

so you're saying that after all this time, there are still sparks in your relationship??

Many years ago my father made a soldering iron from an old veneer iron. The temperature is adjustable from 200 - 500F. He milled a slot in the face of the iron and inset a copper strip. This is one of the best soldering irons that I've ever used.