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Experts,

The last few flights, I've been seeing very high oil temps (yellow and hitting redline).  I noticed as high as 285F.

I changed the oil a few flight hours ago using all Rotax standard parts and procedures (oil level in the tank was just below the top of the normal range).  The engine has about 110 hours on it.

OAT today was about 75F.

In reviewing the video I noticed that one of the CHTs was also swinging wildly and I'm not sure if that is normal/typical.  But, watch the oil temp... :-(

Later in the flight, I had the speed over 100kts and still saw it hit redline oil temp.

Thoughts?

Video: https://www.youtube.com/watch?v=bcOR60d5XE4

Thanks!,

Craig

  • Re: 914 High Oil Temp - With Full Flight Video

    by » one month ago


    Great video.

    Oil presume & head/coolant temperatures remain constant (in the green). This strongly suggests all is well with your fluids.

    My guess, your oil temperature has a bad connection/sensor. Same goes for your right EGT.

    May relate to attitude/air flow thru cowling, causing either a loose connection to move or a wire that has been abraded, to short.


  • Re: 914 High Oil Temp - With Full Flight Video

    by » one month ago


    HI Craig,

    I've watched your video and the first thing that I notice is how quickly the temperature changes. My own experience of oil temperature in a Rotax 912 is that it never changes that quickly. Even if I take off on a hot day it takes a minute or two for the oil temperature to reach its maximum in the climb whereas yours was changing much quicker.

    Seeing how quickly your oil went from 260°F down to 190°F I don't think that this is reporting correctly, unless you have the mother of all oil coolers fitted I doubt that you can get the heat out of the oil that quickly to get a 70°F temperature drop in 15 seconds.

    When I have experienced very high oil temperature I usually find that the oil pressure drops and I notice that yours is relatively stable within a few PSI so I am not convinced that your oil is that hot. In fact when you throttle back in an attempt to cool the oil you can see that the oil pressure actually increases which is what you would expect if the temperature was actually dropping.

    I would therefore suggest that you have an instrumentation problem. The fact that the CHT reading also seems slightly strange then I would suspect either a bad ground, bad connections to the sensors or Garmin or a damaged wiring harness.

    When you did the recent oil change is there any chance that the wiring harness or connections were disturbed? I have seen oxidised terminals on the sensors themselves resulting in poor connection but your aircraft looks too new for that to be an issue.

    Could there be a connection problem in the back of the Garmin? Do the sensor wires connect directly or is there a data acquisition module?

    If you cannot find the cause you could temporarily rig up a thermocouple sensor to a hand-held meter just so that you can verify the temperature independently.

    Let us know what you find.


  • Re: 914 High Oil Temp - With Full Flight Video

    by » one month ago


    Thanks, guys.  I'll look over the wiring tomorrow.  It does seem weird how quickly the temperatures change, but maybe it's possible with the thermostat going "crazy"?  Redirecting the oil flow constantly, perhaps?

     


  • Re: 914 High Oil Temp - With Full Flight Video

    by » one month ago


    I’m seeing the pressure drop when temp goes up and vice versa so even though the pressure stays in the green it tells me that you have readings to take seriously and find why the oil is overheating intermittently and not a faulty instrument.


  • Re: 914 High Oil Temp - With Full Flight Video

    by » one month ago


    I uploaded the engine data from the two flights I took on Saturday where the temps were going crazy.  I don't really see a lot of correlation between oil pressure and temp.  In some cases, the temp is rising and the pressure is rising, but in other cases, they're moving in the opposite direction.

    Interestingly, the CHT2 measurement starts going bonkers when the oil temp starts really rising into the yellow and red zones.

    I've attached two earlier flights where everything is OK and then the two flights on Saturday, where things start to go off the rails.

    33013_2_Screenshot 2022-06-27 203722.jpg (You do not have access to download this file.)
    33013_2_Screenshot 2022-06-27 203807.jpg (You do not have access to download this file.)
    33013_2_Screenshot 2022-06-27 203851.jpg (You do not have access to download this file.)
    33013_2_Screenshot 2022-06-27 203939.jpg (You do not have access to download this file.)

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