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Oil Leak between head and cylinder barrel

in 912 / 914 Technical Questions 12 years ago

  • Re: Oil Leak between head and cylinder barrel

    by » 12 years ago

    Rotax 912 ULS, sn 5646439. I have oil (apparently) leaking from the union between the cyl head and the barrel on cylinder #3 (right side of engine, closest to firewall). When the stud nuts were removed and re-torqued, the two left hand studs were bone dry and the two right hand studs were wet with oil (they either came out with the nut or were were removable with light finger pressure).

    I have reviewed SI 012-019-R1 and find that my engine sn is not covered by the SI. Furthermore, careful review of the SI shows that it applies only to the left two cylinder head stud holes and not the right two cylinder stud holes.

    So, if oil is coming from the right two cylinder head studs, how is that to be addressed? The SI does not cover that specific problem. What keeps oil from getting into the two right stud holes on the 912 engine?

    Thanks.

    Fred
      
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  • Re: Oil Leak between head and cylinder barrel

    by » 12 years ago

    Fred,
    Oil can come from two places: from the inside of the valve cover via the stud (special acorn nut has cutting surface that is supposed to prevent this. Make sure this pretty acorn nut is INSIDE the valve cover)
    Or from a crack in the crankcase. We had on of those a couple of weeks ago. Not sure how it happens as this is a heavily webbed area.
    Put a small amount of blue loctite on the nut and try it (remember to allow for residual oil to seep out) If that does not cure it inspect/NDT the crankcase.
    Rob
      
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  • Re: Oil Leak between head and cylinder barrel

    by » 12 years ago

    Rob,

    Thanks for your reply. Yes, the acorn is inside the valve cover and the acorn was smeared lightly with blue loctite before being torqued.

    Are the right hand studs threaed into blind holes in the cases? If yes, then is the only place the oil is coming from either a cracked crankcase or the head (under the nut)?

    600 hours, TT. No abuse, no overheating, regular oil changes.

    Fred
      
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  • Re: Oil Leak between head and cylinder barrel

    by » 12 years ago

    Hi Fred

    I had a similar problem with mine, 5649049 engine number that had around 300hrs on it. It was one of the first engines with the new crankcase, but with the older type crankcase screws.

    The crank journal screws were allen screws which have been changed to hex head screws now and different torque technique.

    I had oil leaking from all three journals as the bolts became loose and oil was seeping from the high pressure journal oil way and between the crankcase halves and out of the bolt holes.

    This meant that the cases started to fret.

    I have had to strip the crankcase and re seal the faces.

    The bolts you are talking about have two O-rings between the case halves that will need replacing as well.

    I would suggest doing it sooner rather than later as your cases will fret and then the cost will go up in a big way.

    I replaced the case screws with the new type, and the new torque settings.

    Mark.
      
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  • Re: Oil Leak between head and cylinder barrel

    by » 12 years ago

    Mark,
    Thanks for the information. Where was the oil visible on the engine? At the joint between the head and the cylinder barrel or at another location (e.g., crank journal bolts)?
    Fred
      
    Report
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