Two Questions.  On our 2013 912UL the Cylinder Head coolant pipes were removed and unscrewed from the flanges.  They were resealed with the proper sealant and allowed to dry before reinstalling.  We still have a slight seepage on one of the flanges at the threads.  Is there any type of additive (Stop leak) approved to be added to a Rotax 912UL cooling system to remedy this problem? Our mechanic lives far away and I am just looking for a stop gap measure to try.

Second Question:  We have read outs for the water temperature on our panel.  We are showing a temperature of 90F on an 81F day.  Does that sound reasonable and/or should we just be concerned with the oil temperature which is running between 170F and 190F on this 81F day?

William Campbell

Fresno, CA



  • Re: Coolant Temperature 912UL

    by » 6 months ago

    Do NOT go adding aftermarket additives to the Coolant.

    I do not necessarily follow the book to the letter, but that would be taking it too far.

    - - -

    If this doesn't work, you will need to take it back apart and do it again.

    Yeah! I know, It Sucks!  Otherwise, try this...


    Try to identify EXACTLY where the leak is.

    Drain the coolant from the system.

    Redneck a ShopVac to the Coolant cap fitting to form a vacuum on the system.

    Dribble some Denatured Alcohol or Brake Cleaner on the leak until you see it get sucked into the leak.

    That should clean out the leak for the next step.

    Allow the Vac to run another couple of minutes to dry the leak.

    Place a drop of Locktite on the spot and as soon as you see it get sucked in shut OFF the VAc.

    Add another drop to the spot for good measure.  It should wick itself into the leak.

    Now, let it sit overnight before refilling.


    If that doesn't work, you will need to do it the hard, but the correct, way.

    Good luck!

    - - - - -

    Second Answer...

    It this with the engine Running or Stopped???

    The Oil and Coolant temps should be fairly close.  90 and 190 are NOT close.

    90 would be a typical under-cowl temp on an 81-degree day.

    190 would be a typical temp for a running engine on any day.

    Can you clarify the actual conditions?




    Bill Hertzel
    Rotax 912is
    North Ridgeville, OH, USA
    Clicking the "Thank You" is appreciated by all.

  • Re: Coolant Temperature 912UL

    by » 6 months ago

    90C = 194F

    You are probably indicating C on your coolant readout.


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