Hello guys,

 this 912 uls  80 cv suffers oil pump leak as show in the picture.  The owner chenged all the o-rings twice and said it start to leak after 2 years /200 Hr since the o-ring replacement.  The 4 screws are properly torqued and no oil is coming from the gearbox. I'm planning to replace again (the third time) all the o-rings.  What do you think about it ? any suggestion ?  I've seen posts saying to put some Loctite 5910 on the O-rings .  Someone experienced this method can explain better this way ? 

Thank you and best regards


8614_1_20210508_115852.jpg (You do not have access to download this file.)
  • Re: Oil pump leak

    by » 5 weeks ago

    My thoughts would be:

    1. Were the O-rings made of the correct material. i.e. resistant to oil?

    2. Were the O-rings the correct size?

    3. Are the pump housing faces flat?

    4. Is the housing cracked somewhere?

    5. Is something preventing the housing from being screwed all the way down? The screws may be to the correct torque but they may not have pulled the cover all the way down.

    I wouldn't expect to have to put Loctite on the O-ring, it should not need it.

  • Re: Oil pump leak

    by » 5 weeks ago

    Probably not approved, But I have sealed many difficult leaks on engines using Permatex ultra gray sealant, which is pretty much the same as Yamabond from the Yamaha dealer.  My Jabiru fuel pump was leaking oil and the approved sealants all failed.  Ultra Gray has been holding for a long time now.

  • Re: Oil pump leak

    by » 5 weeks ago


    Did he buy the "O" rings from a Rotax service center or just went out and got some he thought would work?

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

  • Re: Oil pump leak

    by » 5 weeks ago

    Never trust what a previous owner tells you!  I'd get in there and put new, proper O-rings on myself and see what happens. You say it will be the third time, but it sounds like it will actually be your first time.

  • Re: Oil pump leak

    by » 5 weeks ago

    I agree with Tyler...  Previous owner may truly believe the mechanic replaced the o-rings, but unless it's logged as such, I would not rely on his or her memory of what the mechanic may or may not have told them they did...  Even if they were replaced, it's pretty easy to "pinch" an o-ring during assembly, especially for someone who doesn't work on Rotax engines all the time.  

    Ditto for Roger's comment:  a "looks about right" o-ring might not be the right material, diameter, heat range, etc. to work properly.  If you want it fixed, get the approved parts and do it yourself.  Better yet, have a qualified Rotax mechanic do it.  Rotax approved parts may not be cheap, but new Rotax engines are a LOT more expensive...

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