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Soldering a radiator...Any tips?

Discussion in 'The Hokey Ass Message Board' started by Bugman, Jan 21, 2004.

  1. Bugman
    Joined: Nov 17, 2001
    Posts: 3,483


    I need to solder a few holes shut in the radiator of our shop car. One in the fins, and a few where the tubes attach to the tank. What type of solder and flux should I use? How do I clean between the fins to get the solder to stick? Anything else I should know? Thanks.

    -Shop Teacher Jeff
  2. McGrath
    Joined: Apr 15, 2002
    Posts: 1,414


    I would use 95/5 Solder. As for cleaning, use "No-Korrode" Soldering Paste after a good Wire Brush cleaning. No-Korrode is fairly aggresive and will clean most stuff that the brush misses during the Soldering Process.

    Soldering holes in the Tubes are sometimes hard to do. Last time I tried it, I ended up Cutting the Tube on either side, right beside the end-tanks, squeezed the stubs closed, and just Soldered them shut near the Tank. Basically, I just bypassed that Tube. I did this with a Jewelers Tip in a Presto-Lite(Acetylene) Torch though. You have to be careful near the Tanks or you will sweat several tubes loose instead of fixing the one that you are working on.

    No amount of Cleaning from the outside can get all the Crap out of the inside of the tubes and it just keeps bleeding through the Solder. Radiator Shops are the way to get it done right because they sweat the Tanks off and Rod the Tubes out before Fixing anything.
  3. I use silver solder.
    I guess if I couldn't get at with a piece of sandpaper I'd use a good acid flux. Be sure and wash it down good with baking soda solution (mix it pretty strong) when you're done.
    Try not to overheat it, especially near the tanks. They are soldered together and will come apart if they have the chance.
    Luck [​IMG]

  4. Paul
    Joined: Aug 29, 2002
    Posts: 15,581


    if you just want it to stop leaking and don't care what it looks like;

    I had a leaking radiator and couldn't afford a new one so

    I pulled it, layed it flat and poured some muratic acid over the area,

    rinsed it real good, dried it real good and forced some epoxy putty in the wound.

    it held till I could afford the new one- about a year later!

    the trouble I've always had with soldering is the area has to be CLEAN,

    it doesn't matter how much I flush it there is always some antifreeze residue and rust inside and it always comes bubbling out screwing up the job.



  5. haring
    Joined: Aug 20, 2001
    Posts: 2,335


    I had a radiator repaired twice with epoxy, and the second time it didn't just leak, it blew out! And antifreeze gushed out of the rad as I sat in stopped traffic on a bridge! Interestingly, because it was in the van, and the engine is beside the driver, I could watch it as it happened. [​IMG]

    I was told the same thing when Iasked about soldering it -- that it's very difficult to get everything clean enough to do it right.

    I had the whole radiator recored for about $200. My van was my daily driver at the time and I needed it to be 100% reliable.

  6. Zeke
    Joined: Mar 4, 2001
    Posts: 1,716


    Not only clean. Needs to be dry too.
  7. CJA
    Joined: Nov 9, 2009
    Posts: 4


    My radiator has a crack around the bottom of the cap neck where it connects to the top of the radiator body. I've srubbed it pretty well with a wire brush, and cleaned it a few times with acetone and will again today with brake cleaner.
    I know I have to get the cracked area hot in order to get the solder to stick.
    I was thinking I'd lay down the solder paste, thick or light coat?, then run a torch quickly over it then immediately get the gun on it and continue to lay down the solder wire.
    Sound alright? I've never done anything like this and am a little scared of screwing up my baby.
    I'm no pro, obviously, and too broke to get any real work done to it.
  8. 1932tub
    Joined: May 31, 2005
    Posts: 405


    Sweat the neck off, clean both soldered areas, neck and tank, tin both sides with 50/50 solder and resweat.
    If there is a crack it will be dirty and you wont get the solder to sweat back under there. Soldering is a capilery joint and it needs solder between two surfaces to be strong
    Good luck!
  9. badsco
    Joined: Jun 11, 2009
    Posts: 104


    Careful with brake clean - seriously

  10. badsco
    Joined: Jun 11, 2009
    Posts: 104


    I de-soldered my top tank as all teh tubes were blocked. Made a tool out of sheet betal to run through them all and soldered it back on with nothing more than a propane torch, plumbers solder, flux and a stainless wire bush to clean it. Takes a bit of time, and dont overheat it - let a pool form and feed it along - too much heat and it sort of drains away. Pressure test at 20 psi and you should be good to go. Fixed a heater core for a buddy and a damaged tube in another rad using the same method - get it shiny clean first and lots of flux. Careful when/where you heat too - you can end up chasing the leak around!
  11. budd
    Joined: Oct 31, 2006
    Posts: 3,478


    i have watched highway truck have there rads repaired, one thing i saw was the guy used a small 90 degree pick, like the kind you use to pull out o-rings, he was working around the tubes and a couple of spots didn't want to bridge, he ran the pick over then a couple times right where the tube met the end plate and the solder took. i fixed my heater core the other week by cutting out the end core and soldering the holes in the tank shut, took a few tried and i used my heat gun to dry it off between testing it in a tank of water, i stuck a piece of rubber fuel line in one of the inlet tubes and held my thumb over the other, i used a pressure regulator set at 25psi and a rubber tiped blow nozel to pressurize the tank.
  12. CJA
    Joined: Nov 9, 2009
    Posts: 4


    So by "sweat the neck off" you mean I should heat it up enough to separate the rad neck from the rad body? how do I do this, torch?
    Then "tin both sides", lay a thin layer of solder on the body hole rim and the neck connecting side rim, and then lay them together and drop my thick layer of solder over crack?

    I may need a step by step drawing too!:D:rolleyes: j/k

    And fellas, Thank you VERY much for the brake cleaner warning. The stuff gave me a major headache last night after prepping to put on my new shoes.
  13. crackerass54
    Joined: Jun 1, 2009
    Posts: 364

    from dallas

    I use regular plumbers solder you get at the supply house, but if you are going to get some flux get C-FLUX, you can only get it at a plumbing suplly house, it's an acid flux, works really well. when you clean parts they need to be down to raw metal, not just no dirt on it, and watch your heat, you can take a radiator from bad to worse really quick

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