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New to Rotax ownership.  My plane has a Rotax 912 ULS (circa 2007 vintage, serial number 5649159).  It lived the first 65 hours of it's life at higher altitudes (Montana) and likely much colder temperatures.  I'm running AeroShell Sport Plus 4 oil, and the standard ROTAX oil filter.  I've flown it about 20 hours since purchasing it, and am just about ready for my first 25-hour oil change.  I had all the hoses (oil, fuel, etc.) replaced as part of the purchase, because they were 13 years old.  I put 16.5 hours on the plane flying it home from Utah to the Dallas area, and had no engine oil pressure warnings.  But when I had time to go through the "settings" on the GRT EIS 2004 system, the oil pressure high warning was set to 90 PSI instead of the 73 PSI I would have expected (normal range is 29-73 PSI according to the Rotax 912 ULS manual).  So I changed that warning threshold to 73 PSI, and started monitoring the oil pressure more closely on the next couple of flights.

Since changing that warning threshold, I've noticed the oil pressure readings seem to be on the high side of the normal range pretty much all the time.  With the lower "warning" threshold, I'm getting occasional High Oil Pressure warnings from the EIS.  My first two flights were very short duration, and I only saw those warnings at idle RPM (or slightly above), with the oil pressure reading as high as 80 PSI near idle, and decreasing as the RPM increased, so that at 3500 or above, it was in the upper 60's.  

On my last flight (which was about 2 hours in duration), the oil pressure seemed to stabilize at the higher end of "normal" range (right around 70 PSI).  But when I decreased the power for landing, the High Oil Pressure warning alerted again, and the oil pressure was reading 80 PSI at near idle RPM.  

I've read through some of the "oil pressure" posts on this forum, and it appears that the most likely culprit is either the sender unit, or the spring/ball in the pressure regulator itself.  I will also check for loose or corroded ground (though the symptoms appear to be reversed from the typical grounding issue).  

Is there anything else I should be checking?  I know people have mentioned that the VDO gauge itself could be at fault, but the GRT EIS 2004 would appear to be working normally for everything else, so I don't think that could be the problem.

Thanks!    – Jim Parker

  • Re: High Oil Pressure?

    by » one month ago


    Here are the most likely 4 things that may cause this and they are all easy to check. With the decrease at higher rpms and increase at low rpms this could just be a poor ground. You may have a ground just a poor one. Take a screwdriver or wrench and tighten all the grounds in the engine compartment and behind the panel. This is more common than you think. The other item could be that before you owned it someone put a shim in with the oil pressure regulator. Just drop the oil pressure regulator screw out at the bottom of the oil pump and look under the spring for a small round shim. While you are doing this buy a new spring and a oil pressure regulator mushroom and replace those two items. If you don't have the current oil pressure regulator plug screw then replace it too. The last thing is it could be the oil pressure sender. My last guess with the symptoms you have. 

     

    My money lies on a poor ground or the oil pressure plug, spring and ball bearing (this gets replaced with the new mushroom regulator) that may have a shim. In the older modles the spring rubbed on the sidewall and caused issues so they changed the plug screw length to prevent that.


    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-574-1080 Home (TRY HOME FIRST)
    520-349-7056 Cell

    Thank you said by: James N Parker

  • Re: High Oil Pressure?

    by » one month ago


    Roger, I will definitely check those four items next time I'm out there.  I'll start with the grounds, then see if there is a shim installed (and remove it).  If neither of those is the issue, I'll have to order the ball (or mushroom) and a new spring.  

    Is the mushroom an improvement over the ball, or just a different solution.  I'm asking because the mushroom costs $33.10, while the ball costs only $1.29.  If there's no functional difference, the ball option looks pretty good!  LOL


  • Re: High Oil Pressure?

    by » one month ago


    Many that have gone to the mushroom says it helped them. i like it better than the ball bearing. Not sure why Rotax just doesn't do it right from the factory? That's above my pay grade.


    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-574-1080 Home (TRY HOME FIRST)
    520-349-7056 Cell

  • Re: High Oil Pressure?

    by » 3 weeks ago


    Just updating this thread after making several checks...  

    1) I loosened the screws and cleaned off the connectors for the single wire connecting to the oil pressure sending unit.  I assume that's the "positive" and the ground is done through the engine?  Once all the grime and moisture was removed (not much, but some), I reinstalled and tighted the connections firmly.

    2) I removed the pressure regulator screw and checked for the presense of a shim (none present) and checked the spring for any flat spots or wear indications (there were none).  But the regulator screw is the old type, so I've ordered a new regulator screw, spring, and ball and will replace all three when they get here.  The "mushroom" (replacement for the ball) is back-ordered everywhere I could find, but when it eventually arrives, I will replace the ball with the mushroom.

    3) After all this, I did a runup, and confirmed that the oil pressure is now reading between 52 and 55 psi from 3500 RPM to redline.  And today, I went for a flight:  0.9 hours in the pattern, doing stop-and-go landings to improve my technique.  Oil pressure stayed well within the normal range the entire time.

    So, thanks to you, Roger Lee, for excellent advice on what to check!  You nailed it! 

    I'm loving my "new to me" RANS S-6ES Coyote 2, with Rotax 912ULS and Warp Drive 3-blade G/A prop...  Performance is pretty amazing!  Today the wind was blowing 90º to the runway heading, variable betwen 0-8 knots, so no headwind at all.  Yet I was still consistently landing and coming to a stop within 250 ft of my touchdown aim point, and getting off the ground less than 200 ft from my stationary starting point.  And climbing 750+ FPM at 70 MPH makes for one heck of a steep climb gradient!  

    I kept trying to get an accurate reading of the static RPM to check my prop pitch setting, but I was airborne so fast it never hapenned.  LOL


    Thank you said by: RotaxOwner Admin

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