Cracking exhaust manifold

Engines, Exhaust and Fuel Systems

  1. SixBanger

    SixBanger Well-Known Member

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    Time to take off the manifolds to fix that exhaust gas leakage. Find out that the exhaust gasket between the intake and exhaust was gone. Also have to fix a threat in the ex manifold it was broken for years.
    But I have notice a crack in the exhaust manifold. See this is a common problem on the /6 manifold.
    I want to try to repair this before getting something different for exhaust.

    I saw that is likely possible to weld the cast iron manifold with fillers. Can try this to weld with TIG and fill the manifold with sand to keep the heat and to and ensuring that it cools down as well as possible.
    Also it is an possibility to fill up the crack with JB weld.

    I do doubt which method delivers the best results.

    Thanks!
     
  2. Aspen500

    Aspen500 Well-Known Member

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    JB Weld won't work. The heat will cause it to melt and burn. Don't ask me how I know this, lol.
    You're correct, S6 manifolds cracking is a very common problem.

    To weld cast iron, you need to first "V" the crack and drill a small hole at each end of the crack, to keep it from cracking further. Then the area you are to weld needs to be preheated to 500-1,200 degrees F (about 260-650 C). The weld area must be cleaned spotless and brushed with a stainless wire brush. This removes the graphite on the surface. Then use a high nickle content electrode for stick welding or filler rod for TIG. Once the weld is complete, don't let it cool too quickly or it can crack again.
    I learned how to do it in high school but, that was 37 years ago so my memory may be a little fuzzy on the exact procedures.

    Here's cast iron welding guideline thing I found:
    Welding Cast Iron | Lincoln Electric
     
  3. SixBanger

    SixBanger Well-Known Member

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    Many thanks for info and tips. Great I would try the preheat methode, using an autogenous burner to pre-heat it.
     
  4. Aspen500

    Aspen500 Well-Known Member

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    Autogenous burner?

    At any rate, it can be welded without preheat but then there's a big chance it will crack right next to the weld.
     
  5. SixBanger

    SixBanger Well-Known Member

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    Ah, here we call it 'autogeen lassen' I was thinking Englisch translation is autogenous welding.
    I mean using the oxy acetylene welding tool as a heater.
     
  6. Aspen500

    Aspen500 Well-Known Member

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    Got it! I figured it was something that got lost in translation. Reminds me of when I was dumb enough to be an Audi tech at a dealer here. The service manuals are translated from German and sometimes, it doesn't translate. You read it, read it again, read it another time and go "WHAT?????????????" :eek:

    An oxy-acetelene torch will work as long as you have a "soft" flame. Hope you know what I mean by that. It would help a lot to have an infrared thermometer capable of reading between 500 and 1,200 degrees F to monitor the temp so it's hot enough, but not too hot.
     
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  7. AJ/FormS

    AJ/FormS Well-Known Member

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    My backyard BBQ cooks my steaks at 450F on low.
    If I crank it up a lil afterwards to burn off the grease, the air-thermometer can rise to 1000F fairly soon after.
     
  8. SixBanger

    SixBanger Well-Known Member

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    Translating technical words from actions or objects can sometimes be difficult.
    But indeed German translation can be quite difficult. Sometimes they describe an action quite extensively while the core can be explained in one sentence.
    I have a workshop manual of an RD250 in German (also bike came from Germany). It appeared to be that a nut from the exhaust could be used to dismantle the flywheel. This also had fine wire. Good tip, but I had to read the text a number of times lol!

    AJ/FormsS Speaking off BBQ and steaks. If this welding job fails. There is always an option to use the manifolds as an DIY steak griller.
    And get some decent headers, but yeah it is a nearly std slant and this should not improve lot of performance I can imagine.
     
  9. Oldiron440

    Oldiron440 Well-Known Member

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    About 15 minutes per side till the just pink in the middle.
     
  10. SixBanger

    SixBanger Well-Known Member

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    I cannot say for sure that the steak is still red/pink and juicy after 15 minutes per side. 15 seconds earlier.
     
  11. SixBanger

    SixBanger Well-Known Member

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    I just have to say that it currently makes no sense to weld the manifold.
    My dad wanted to help with the removal of the broken bolt in the manifold. However, the left tap broke and I cannot drill it out with a cobalt drill. I have no idea if I can still get it out.

    Can happen, but now looking for another manifold.

    Saw that in Belgium a volare with / 6 is still on the demolition. Maybe take a visit there. Or ebay manifold / or upgrade to a clifford header.
     
  12. Oldiron440

    Oldiron440 Well-Known Member

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    I thought we were BBQing castiron at 500°+
     
  13. BudW

    BudW Moderator Staff Member

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    If you find a good exhaust manifold (which are out there), generally it is best to leave it attached to the intake (if possible). The three fasteners that hold both manifolds together, can be . . . troublesome on removal or reinstallation.

    The good news is all /6 factory exhaust manifolds are the same, except for the ones with EGR valve – which will interchange (either direction) with minor modifications.


    I’ve heard the weld holds better if you can weld it bolted into position (like attached to a cylinder head) – but not sure how one would do that, exactly, especially when welding when hot.
    I have no experience welding cast iron (or any kind of welding) - so i might not be best one to say anything.


    The (Dodge) Cummins inline 6 diesel exhaust manifolds have a similar cracking problem. There, the aftermarket has come out with a solution to cracking. It allows for heat expansion/contraction over its width. Basically it changes from a 1-piece manifold to a 3-piece manifold. The two connectors are tapered and inner taper expands more than outer taper does for a seal.
    BD 5.9L Exh Manifold .png
    It would be nice if someone made a version for /6’s.
    BudW
     
  14. 89.Fifth

    89.Fifth Well-Known Member

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    I've been told by numerous people that brazing a cast iron exhaust manifold is a lot more successful than welding.
     
  15. SixBanger

    SixBanger Well-Known Member

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    Ordered a new manifold from ebay. For now I have weld an bolt to the exhaust to hold the intake. It was lost anyway. Hoping it will stay intact in the few weeks.

    I like that 3-piece manifold.