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Oil Pressure Drop on Take-off - SOLVED!

in 912 / 914 Technical Questions 6 years ago
Hi Guys,

So I have a 2008 912 ULS with only 300 hours on the clock, and I have an issue that has me scratching my head.

My oil pressure ( and temp for that matter) is always low, and on take off, it's scary low.

So when I take off, it drops to below 30Psi - Maybe 20 or so. Then once I roll the throttle off a little it climbs back up to sit at just over 30, where it sits the entire flight. Even in idle on the ground it sits there.

The oil temp never gets over 75 in the cruise (yellow) and will only ever get to the green on a decent climb under power.

Any ideas? I have read everything from bad ground wire, to a dodgy sender - but same have changed the sender and the oil gauge itself, and it's still the same.

See pics - One is on take off ( the low one) and the other is the cruise.

Thanks in advance.
John
IMG_4880.jpg (You do not have access to download this file.)
IMG_4882.jpg (You do not have access to download this file.)

  • Re: Oil Pressure Drop on Take-off - SOLVED!

    by » 6 years ago

    Is this a new or chronic issue?
    What was the typical pressure and temp for the first 300 hours?

    It is time to determine if the readings are correct or the values are actually low.
    Remove the Oil Pressure Sender and replace it with a basic mechanical gauge with a needle dial.
    Start the engine and monitor the gauge from a short distance away.
    CAUTION! Do Not stick your head in the spinning propeller! :ohmy:

    Once the engine has heated up all that it usually does, stop the engine and remove the cap from the oil tank.
    Pull the Dip Stick and insert a Kitchen thermometer in the Oil.
    The Oil tank is before the Oil Cooler so it should read slightly higher than the panel gauge.

    If the external gauge and thermometer match the panel instruments, the numbers are real.
    Otherwise, it is a measurement problem.

    Bill Hertzel
    Rotax 912is
    North Ridgeville, OH, USA
    Clicking the "Thank You" is Always Appreciated by Everyone.

      
    Report

  • Re: Oil Pressure Drop on Take-off - SOLVED!

    by » 6 years ago

    Now that is an awesome idea! :)

    Thank you! Talk about not seeing the forrest for the trees.

    The pressures and temps have always been low, but I have never noticed the drop on take off before. Because I myself am only 100 hours in, during take off, I was not looking at instruments other than RPM, AS, and ALT (They are right in front of me) until I rolled off the the throttle a little after the initial climb, and then scanned the right hand side of the panel. The Pressure had somewhat rebounded since then - So I am not sure.

    I have some videos from a cockpit mounted camera behind me early on... I will dig them out and see if it can reveal anything.

    I will look to getting a gauge to test - Do you already know of a solution that works, to save me the investigation on connections etc?

    Thanks very much for your help!
      
    Report

  • Re: Oil Pressure Drop on Take-off - SOLVED!

    by » 6 years ago

    If Bill's solution doesn't work try this.

    If the oil pressure decreases every time you increase the throttle and goes back up when you reduce throttle replace or tighten the ground wire. I have seen a number of these. The first one I ever saw way back when took me a couple hours to troubleshoot. I finally took a jumper wire and bypassed the original ground wire and problem solved. If you have a poor ground the pressure will change.

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

      
    Report

  • Re: Oil Pressure Drop on Take-off - SOLVED!

    by » 6 years ago

    ... I will look to getting a gauge to test - Do you already know of a solution that works, to save me the investigation on connections etc?


    Well, there is good news and bad news.

    The Good News is that a 70-100psi gauge is inexpensive and easy to come by.

    The bad news is that the gauge will probably have a tapered 1/8" NPT Fitting. (Common in the U.S.)
    and that the sensor you will be removing and the port on the Oil Pump is a Straight Threaded M10x1.

    The two thread are very similar and will happily cross thread without much effort.
    Don't do it though, or you will soon regret it

    The Good News is that this is a common problem encountered in the automobile industry and an NPT to M10 adapter should be readily available Online or at any decent auto parts store.

    If the gauges in OZ are already M10 then you are golden!

    Bill Hertzel
    Rotax 912is
    North Ridgeville, OH, USA
    Clicking the "Thank You" is Always Appreciated by Everyone.

      
    Report

  • Re: Oil Pressure Drop on Take-off - SOLVED!

    by » 6 years ago

    Thanks Guys,

    I will look into it over the next couple of weeks. We are heading into Winter here too, so makes keeping the oil temp up difficult. I put tape over the cooler last year which seemed to help a little.

    OK - Back to the ground.... Are we talking the ground wire on the back of the Gauge? Or a wire on the sender? Could someone please clarify?

    Cheers
    J
      
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