Soldering & Desoldering Heater Cores

[FishaOfMen]

I just bought a Fedco 2-342 heater core (from AutoZone for $17.99!) and want to attach some hose barbs to it. I’ve done this a couple times in the past with a Dremel and some good epoxy, but this time I want it to use solder and make it look really good. For the moment, I’m hoping to install some ¼” female threads like on the DTek cores.

What I want to know is if you guys have any tips when it comes to soldering and desoldering on these cores. Because the whole core is held together by solder, it seems that one could create a leak pretty easily. I have a little soldering experience. I have a 30W iron that I’ve used for some volt-mods, but I’m unsure of myself when it comes to auto parts … and I sure as heck don’t want to make my core leak!

I’ve seen some really professional jobs around here. For instance, there’s mad mikee’s 2-342 where he removed the tubes from the core by heating up the solder and pulling the tubes. He then soldered pieces of the tubes back in. I want to do something like that. All help will be appreciated.

[Dnallom]

I used an epoxy metal 2 part mix, that i also used to repair rivets on my aluminium boat.
I was hesitant about using heat of any kind on the radiator.

[Khledar]

Well I don't think you'll have much success using a soldering iron.(EDIT: I'll explian why, you have to heat the metal up to the melting temperature of the solder, the more mass of the material the more heat you need to get any part of that material to a given temp. One little wire is a very small thing to heat up, a large chunk of brass specifically designed to dissipate heat is not so easy.)

I've never put female threads(only done male) on a core before but, you'll definately need a torch. The solder used in keeping the core together is usually a high-heat solder, obviously designed to take the heat of your vehicle's coolant (can be rather hot) + a safety factor. I've never had a heatercore just, fall apart while torching it- or leak - I've only ever fixed leaks with solder. As long as you keep the torch pointing generally tword the brass tanks while you do it the rest won't get hotter than standard operation. But precautionarily:

1) Use rosin core low heat solder.
2) Don't leave the torch on unneccesarily, if you have both surfaces soldered up, attaching them only takes a second after the solder melts.

I dunno just using a strandard propane torch I've found myself rather impatient so I'll just crank up the torch and heat the sucker up to do my soldering - never had any problems but nothing prolonged prolly never had the heat on for more than a couple minutes at a time, heat her up solder on - let her cool.

[bigben2k]

Remember to fill the core with water, to prevent anything else from desoldering.

Worked for me (see sig).

[V12|V12]

I was going to say the same thing as BB... WATER is that key and plenty of it, just WATCH OUT for the BOILING steam that will soon be errupting from the inlet/outlet! And if you're really concerned, when I added diff barbs, I put cold water in AND placed on the stove top's metal surface plate to dispate even more heat, And besides, the brazing (solder in your case) metal they use (old tin lead mix), (Newer silver antimony/tin etc) melts a around 700F for the fins, not all, but the one's I've tried, so the solder or brazing material you'll be working with will have a safe melting cushion of about 3-4ooF before you have to worry about unbinded joints etc... But ALWAYS direct the heat up and at the point of bonding... and last but certainly NOT EVER EVER least, please wear some EYE PROTECTION! That flux LOVES to pop and splatter and you don't want it in your eyes... Good luck!

[FishaOfMen]

Great advice guys. I'll have to go out and get a torch and give it a try. I'll be sure to let you know how it works out.

[bigben2k]

One more tip... the water level really can't go up to the joint that you're soldering: it can interfere with your soldering job, and you'll have a leak. Not that you'd be able to solder with water at that level...

I remember the splatter...

[Gooserider]

I also modded my 2-342 (actually the equivalent NAPA Belkamp #, but that shouldn't matter)

My technique was similiar to that described above, and is essentially the same used in working with any sort of copper plumbing. If you have never soldered plumbing with a torch before, it would probably be a good idea to get a short bit of pipe and some fittings and practice a bit to get a feel for doing it.

As mentioned earlier, eye protection is extremely important, and also make sure you have removed any flammables from the working area - Murphy's law says that if there is anything that will be set on fire or damaged by a torch within six feet, the torch will set it on fire or damage it!

I put a plumbers union (female side) on one end and on the other I cut off the long tube that comes out of the rad, trimmed most of the bent bits off, and then used a nipple to splice the straight part with the flare to 3/4" back on so that I'd have a straight inlet pipe almost 120mm long (so I can get around a fan)

I used solid core TIN/LEAD solder *NOT* the new higher temp stuff that you are supposed to use on potable water plumbing. (It is now illegal in the US to use lead solder on drinking water plumbing) The Tin/Lead solder has a lower melting point. In addition I used plenty of plumbers acid core solder flux (not electronics rosin flux)

I very carefully flaired and straightened the ends of the tubing coming out of the rad until I had a good snug (not tight) friction fit on my fittings, then used emery cloth to clean and shine all contact surfaces. This is VITAL, the solder won't stick unless the surfaces are totally clean!

Then I filled the rad with cold water to just below the level of the tank / pipe join - this put about 3/4" of space between the water level and the end of the pipe I was soldering on.

Then I did a final cleaning pass on the solder surfaces, and brushed a good layer of flux onto each surface, making sure to cover all of the copper. After I had done this, I slid the fitting over the pipe to it's final placement.

I then carefully heated the junction with a propane torch (I have a hand held torch with a hose that attaches via an adapter to a 20lb BBQ grill tank) until the flux started to smoke, and touched the solder to the junction on the opposite side from the flame. When the joint is hot enough, the solder will melt and wick up into the joint. Immediately remove the flame and gently wipe the excess solder off the joint with a rag or paper towel.

I repeated this with the other fitting on the opposite end and it was done.

Notes...
1. It is important to put the plumbers union together before soldering. This keeps the solder from possibly getting onto the join surfaces, and keeps the female side nut out of the way. After the joint has cooled, dissassemble the union and use the male part on the rest of the project.

2. When I was using the nipple to attach the cuttoff pipe extension, I first soldered the nipple onto the peice of pipe, (using the same techniques except I didn't bother with the water) then fastened the assembly to the radiator. This minimized the amount of heating done to the rad.

Hope this helps...

Gooserider

[V12|V12]

Hey one more little trick that I discovered while brazing my waterblock together... If you want to have some control over where the solder bonds, try coating a side with PERM marker (Sharpie) and it'll smoke a little till it's solvent free, but watch as the brazing material magically stays unbonded to the perm-marker side! Works really well for controlling flow of the solder and can removed with alcohol or some other solvent.... Remember EYE protection!