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I need your combined experience to help solve a problem I have with my 912A.

The engine runs very nocely. Smooth, good power, reliable as can be. However, I'm using oil at about 4 ounces every 3-4 hours. The engine has great compression, and the differencial pressure readings are 79-80, 80-80, 80-80, 80-80.

The engine does not visibly smoke, but oil consumption is consistent.

I'm currious as to what may be the problem? Where do I continue to look? I've checked the cylinder walls with a scope, they look fine.

I'm wondering if a cracked oil control ring might be the source of the consumption.

Thoughts?
  • Re: Oil Consumption Puzzle

    by » 11 years ago


    Hi Alex,

    If the compression test is good, the plugs are clean and not oily and no oil in the exhaust then you have a leak somewhere you haven't found. Look externally not necessarily internally. Most oil use on a 912 is a leak some where and usually the high flow air blows it off the leaking part so sometimes it's a little harder to spot. If it is a pusher look at the prop and see if it has any oil on it.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell


    Thank you said by: Alex Loewen

  • Re: Oil Consumption Puzzle

    by » 11 years ago


    Thanks Roger,

    I wish it was an external oil leak!!!

    I've had this puzzle for a while... While the engine is not smoking (visibly), my landing gear turns black from the exhaust. (Just thinking out loud, but I should be looking at each exhaust port to see if there is any oil residue to be found.... and which cylinder is it coming from).....so I know the oil is coming through combustion.

    Based on all the "non-invasive" tests I've done, the engine shows well. It runs well. The spark plugs look good. That's why I'm guessing at the oil ring. In another application (Ford automotive engine), I've seen oil consumption as a result of a broken oil control ring, and the compression was 100% OK. That's why I thought I'd ask the question before I take the engine apart to check.

    Cheers,
    Alex

  • Re: Oil Consumption Puzzle

    by » 11 years ago


    I thought I would update the forum on this subject....

    I removed the cylinders, and no surprise, the oil ring was completely gummed up.... I'm guessing the previous owner used Av gas for too long. I replaced all the rings, and my oil consumption has gone to near zero.

    I've included a picture of the oil rings for your viewing pleasure (old vs new)


    Cheers,
    Alex
    rings.jpg (You do not have access to download this file.)

  • Re: Oil Consumption Puzzle

    by » 11 years ago


    Nice job and good catch.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell


  • Re: Oil Consumption Puzzle

    by » 7 years ago


    Hello,
    I have the same problem. So all I need to do is remove the head and cylinder and replace the oil ring? I have no external leaks? Great compression and runs great.

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