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ENGINE OIL INCREASING ABOVE MAX

in General Tech Discussion 13 years ago

  • Re: ENGINE OIL INCREASING ABOVE MAX

    by » 13 years ago

    Have you put a mechanical gauge in line for the oil pressure to compare to your plane?(for diagnostics) Oil pressure senders do go bad often. If the oil pressure kicks up and down you may also have a bad ground.

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

      
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  • Re: ENGINE OIL INCREASING ABOVE MAX

    by » 13 years ago

    Gentlemen

    May I suggest another potential factor that could be contributing to the fluctuating oil pressure issue and that is the oil itself!

    A few years back Rotax removed some of the originally recommended oils from their SB on General Operating Tips(copy available in SB section of this web site) due to a problem with these oils "hanging up" in the engine! The problem supposedly evolved from some of the oil manufacturers making a secret formulation change to meet new emission requirements that compromised in some cases not only the Anti Foam ability of the oil but also the oils ability to flow without over adhesion to internal engine parts. Oils that had worked good prior to this event all of a sudden didn't! This is one advantage with the New Aero Shell Sport oil, they have committed to Rotax to "never" change their formula without consulting Rotax first!

    I saw this situation demonstrated at a Rotax Service School I attended at the Canadian Rotax Distributor "Rotech"( www.Rotech.ca ). There they have an engine test rig were they showed us how certain oils "hang up" in the engine disrupting the return flow of oil from the engine sump to the oil tank! Basically these oils are too "sticky" and in some cases to "Airated or Foamy" resulting in them sticking and congealing inside the engine disrupting the steady return of oil to the oil tank. Rotech's rig has transparent oil lines allowing one to visually watch the actual flow of the oil to and from the motor. As well they have an oil level sight tube on the actual oil tank allowing you to watch the level of oil maintained in the oil tank itself as the engine is running at different RPM's. Lastly they also monitor the crank case pressure, suction vacuum on the oil circuit feed side to oil pump and of course oil pressure. This setup clearly demonstrates how certain oils just don't flow consistently back to the oil tank but rather build up in the engine and then sporadically flow back inconsistently. This condition can result in fluctuating oil tank levels and pulsating oil feed supply back to the oil pump resulting in(but not limited to) fluctuating oil pressure!

    Another demonstration Rotech performs to show this condition is with simple gear device often used by some of the so called "Super Slip" oil companys who like to use this demonstration device to show how well their oil or additive works in "hanging on" too the gears themselves. Basically the demonstration device has two separate compartments each with three plastic gears turned by their own hand cranks. One compartment has the "Super Slip" companies oil or additive, the other compartment an off the shelf standard automotive oil. The demonstration is designed to show just how well the "Super Slip" oil or additive better adheres to the rotating gears over that of the standard automotive oil. You can clearly see how the "Super Slip" oil wicks up out of the resivour onto the gears were as the standard oil has a much thinner film of oil, much less wicking and a much fuller resivour.

    The technical advantage these oil or additive companies try to promote with this demonstration is exactly what you want to avoid with many engines, especially any engine with a gear box like a motorcycle with combined engine oil for crankcase and transmission, but more importantly your dry sump Rotax engine itself! As your Rotax has a gear box, these type of oils get hung up in the gear sets and other parts of the engine resulting in the inconsistent oil flows I've mentioned above!!

    To further add to the problem, people who might be using these type of oils or additives in their Rotax, who do not carefully "purge" the oil sump by "burping" the oil tank as demonstrated in the Rotax-Owner video on the subject ( See Oil Check Procedures Video in the video section of this site: http://www.rotax-owner.com/information-reg/expanded-video-instructions-reg/36-exp-si-912-018 ), can easily overfill the system with oil. As these "Super Slip" oils and additives don't easily return back to the oil tank from the sump but rather "hang up" in the engine, especially cold, it sometimes can be impossible to get an accurate oil level check!

    Lastly, combine this bad oil issue with a restrictive oil circuit due to bad connection joints, lines and/or oil coolers and your going to have a real problem on your hands!

    In summery, only use oils on the recommended list, never use additives, make sure your oil lines, fittings and cooler are all properly qualified(the system doesn't exceed maximum allowed suction values as stipulated by Rotax), and your engine will thank you for it!

    Hope this helps some of you......good flying.
      
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  • Re: ENGINE OIL INCREASING ABOVE MAX

    by » 13 years ago

    Thank you Ralph.
    Unfortunately, the oil I'm using is the Aeroshell Sport.
    But I suspect that the oil pressure fluctuations are unrelated to the issue of increasing level as they are most likely caused by some problem in the pressure transducer or in the cabling. I will run a check in this area first.
      
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  • Re: ENGINE OIL INCREASING ABOVE MAX

    by » 13 years ago

    Just a side note.

    Ralph is absolutely right on oils. All oils aren't good in Rotax engines. The problem has arisen in our engines from time to time over the years. Years ago Rotax changed the oil dip stick so it allowed a higher volume of oil in the tank. This helped with foaming oils and from people allowing low oil levels. The old dip stick has a round top handle where as the newer dip stick is square. Make sure you have the square dip tick handle. Don't run your engine with the oil at the bottom of the dip stick mark. Second some oils do foam a lot more than others so that is just one reason to make sure you use the proper oil that has the least foaming characteristics. This allows air into the system which not only could cause the oil gauge fluctuations, but can and will cause damage to the engine. Another issue is acidic build up. Some oils do a lousy job of keeping acid content at bay. This can and will cause pitting in many areas of the engine and some of it can be severe. Rotax has a list of approved oils in their paperwork. Rotax in no way can test all oils in the world. Are there other good and maybe even better oils out there, absolutely, but you need to do your homework to make sure. Not all oils are available in all areas of the world. Using a semi or full synthetic should be your goal and not use a straight dino based oil. The synthetic oils can handle the stresses within our engine from high to low temps, shear, acidic control, stabilized viscosity, ect... much better.

    Oil is the blood of your engine, don't disease it or it will shorten it's life, just like a person.

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

      
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  • Re: ENGINE OIL INCREASING ABOVE MAX

    by » 13 years ago

    Thanks to you too Roger.
    Yes, I confirm I have the dip stick with the square handle.
    What it's really puzzling is that I've been running this engine for more than 500 hours using always the same fuel and oil without any glitch whatsoever and, all of a sudden, this happened (and, as I said, I'm in "good" company as this issue is affecting several engines here in northern Italy).
      
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