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Hi everyone. The Sight glass on the side of the expansion tank has a small leak. Over 25 hrs of flight time it has been bleeding out the overflow tank very slowly. Occasionally enough will weep out and build up to drip onto the crankcase. I was able to capture this video while doing a prop balance at my house and while the engine was hot. When the engine is cool, it doesn't leak. Prior to this I knew I was losing coolant but I couldn't identify where exactly.

Does anyone have suggestions on how to repair this? Or should I just let it continue to leak and clean it up every 10 hours or so?

The Rotax Pubs don't have any anatomy of the sight glass or how to deal with a small leak like this.

Video Link Below:

https://youtu.be/3ewil-q99Sc

  • Re: Leaking Sight Glass (Video Link)

    by » 5 months ago


    I would try Tightening it slightly first.
    If that doesn't work, replace the crush washer. 


    Bill Hertzel
    Rotax 912is
    North Ridgeville, OH, USA
    Bill.Hertzel@Yahoo.com
    Clicking the "Thank You" is Always Appreciated.


  • Re: Leaking Sight Glass (Video Link)

    by » 5 months ago


    If tightening doesn't work take it out and apply a sealer on the threads.


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


  • Re: Leaking Sight Glass (Video Link)

    by » 5 months ago


    Any idea on a part number for the crush washer? Im not sure where to look for that sort of information.

     

    @ Roger: do you think Loctite 567 would work? Ive got some leftover from the brake line fitting assembly I did earlier in the build.

     


  • Re: Leaking Sight Glass (Video Link)

    by » 5 months ago


    567 should be Good.
    Try tightening it a Half-Flat first.
    Is this on the Expansion or the Overflow Tank?  They are two separate items.
    What Aircraft is this on?
    Is this tank a Rotax Part?  Part Number ???


    Bill Hertzel
    Rotax 912is
    North Ridgeville, OH, USA
    Bill.Hertzel@Yahoo.com
    Clicking the "Thank You" is Always Appreciated.


  • Re: Leaking Sight Glass (Video Link)

    by » 5 months ago


    Hi Bill!

    RV-12iS. Rotax 912iS. 

    This is the Rotax expansion tank as depicted in the attached picture below. Not the overflow tank. 

    I tightened the sight glass as yall suggested, but havent had the opportunity to test it yet. The key thing to see in the video I originally filmed, is that the leak is not coming from the screwed in sight glass, its coming from the inner ring that the sight glass screws into. The inner ring that seats into the expansion tank itself. Very strange. 

     

    Again not much in the publications about it, but im hoping to avoid having to buy and install a new expansion tank!

    32008_2_expansion tank.PNG (You do not have access to download this file.)

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