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Thread: Exhaust leaks

  1. #1
    CamTom12's Avatar
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    Default Exhaust leaks

    In what seems like a never-ending spell of bad luck, it looks like my exhaust is leaking around the flanges.

    First discovered when I switched my CHT monitoring to a system that uses grounded probes (from ungrounded), and I saw a significant increase in CHT from previous flights in similar conditions.

    I went through all the troubleshooting steps with the manufacturer and it doesn’t appear to be an installation error.

    Here’s some pictures:

    #1


    #2


    #3


    #4


    From folks with experience, does this look like a situation where resurfacing would likely be required?

    I have no-blo gaskets and new studs/washers/nuts on order. Anything else I should be thinking about?
    Last edited by CamTom12; 10-30-2019 at 09:41 AM.

  2. #2
    Administrator Steve Pierce's Avatar
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    Default Re: Exhaust leaks

    Is that soot or cooked paint? Hard to tell in the picture. It has to leak really bad to erode the mating surface. Can't tell from your pictures but doesn't look like it.

  3. #3
    CamTom12's Avatar
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    Default Re: Exhaust leaks

    Quote Originally Posted by Steve Pierce View Post
    Is that soot or cooked paint? Hard to tell in the picture. It has to leak really bad to erode the mating surface. Can't tell from your pictures but doesn't look like it.
    I think itís just soot, but I havenít tried cleaning it up yet. Iíll get some better pictures when I take it apart.

    Would it mean anything worse if the paint was cooked?

    Thanks!

  4. #4

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    Default Re: Exhaust leaks

    Cooked paint I think is common, we painted an O-300 and it cooked the paint the first flight, runs fine, just watch your cht if you have them. Exhaust leak needs fixed or it can be an expensive repair or new cylinder... just had to put a new one on because previous owners let an exhaust leak go to long.

    The cooked paint looked burnt orange kind of like what you have there.
    Last edited by SMO22; 10-30-2019 at 10:19 AM.

  5. #5

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    Default Re: Exhaust leaks

    Wo just saw the take it apart comment... why do that if its running well? I would wait for a very experienced mechanic to check it out before getting the wrenches out!

  6. #6

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    Default Re: Exhaust leaks

    I have had to replace my exhaust gaskets on PA-22-150. I was definitely able to tell that the exhaust gasket was leaking due to the fact that you can see it. The pictures I am seeing look like burnt paint, not a exhaust leak. I even had exhaust soot on the outside of the cowling. If they were new when you put them on I would do a little more flying and just keep checking them. Keep an eye on the CHT if they are steady I would not worry about having a exhaust leak unless you can see the carbon tracks.

  7. #7
    CamTom12's Avatar
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    Default Re: Exhaust leaks

    My understanding was that the white dusting signified a leak.

    My CHTs in the 3 cylinders with the most dusting (1, 3, & 4) read in the low to high 390s in cruise (2500í and 50-ish OAT). The other reads 350-ish.

    EGTs (I know, fairly worthless) are all within 70 degrees at cruise - some power settings are within 50į of each other.

    My cowl pressure differential is pretty close to Lycomingís requirements, and my new CHT monitoring system has been thoroughly troubleshot.

    Thatís why I started looking at exhaust leaks: I was told they can contribute to erroneous CHT readings.

  8. #8
    Glen Geller's Avatar
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    Default Re: Exhaust leaks

    Tom,
    Soot will usually wipe off on a clean white cloth, and look pretty obvious.
    Then flying a few hours will re-soot that cleaned surface.
    If they are leaking, it's not a terrible job to replace them.
    Before you take off the exhaust, mark the suspect areas with a grease pencil.
    Then you can take a good straight-edge to the face of the flange(s) and inspect for flatness.
    Dragging a light file across the face will show where it's high, that might match your leak.
    Some mechanics advocate a well-placed hammer WHANG! to mating face of the mounting ears to correct a slight bend that caused a leak.

    Good luck!
    GG

  9. #9
    Administrator Steve Pierce's Avatar
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    Default Re: Exhaust leaks

    Cameron, I would check per Glen's post. Soot will wipe of. Burnt paint around the exhaust port doesn't concern me but when it is further across the cylinder head I start investigating. Yours don't look bad but I do have an exhaust flange resurfacing tool that can resurface the exhaust flange on your cylinder head that does a very nice job and doesn't requiring removing a cylinder.

  10. #10
    CamTom12's Avatar
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    Default Re: Exhaust leaks

    Glen and Steve, I'll do just that and report back. Thanks for the help!

    This (https://www.tennesseeaircraft.net/20...se-and-effect/) is what I had read to make me think my higher CHTs might be caused by exhaust leaks - am I heading down a valid troubleshooting path in your opinions?

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