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Condensation in Oil Vent Tube

in General Tech Discussion 9 years ago
Aloha Rotax Owners,

I've been flying a 912 ULS in Hawaii for about 150 hours, one whole year now. Just today, I noticed heavy Condensation in my clear oil vent tube line. I did not fly today, but just did some run-ups on the engine. After about 15 minutes, I noticed drips of oily/water slowly and intermittently trickling from the vent tube from the condensation build up. I just switched to 100LL instead of 92 Mogas since I just do warm-up every 7-10 days since my aircraft is grounded for now. Are these watery drips from the oil vent tube normal? Oil level seems to be where I left it since I noticed this occurrence. Hawaiian weather a factor?

Mahalo all for your input,
Eric
(808) 222-9492

  • Re: Condensation in Oil Vent Tube

    by » 9 years ago

    Hi Eric,

    In a warm humid climate that would be normal. As the oil gets hot it cooks off moisture inside the tank and it will condense in the tube and can drip if there is enough of it. The oil tank vent tube is the engine's only breather. Moisture or other contaminants is why we want to let our oil get hot to help cook these off. As heated openings cool they can draw in cooler air and that may be moisture ladened.

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

    Thank you said by: Eric Nakamoto
      
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  • Re: Condensation in Oil Vent Tube

    by » 9 years ago

    It's been unusually warn and humid lately.
    Thank you Mr. Lee. Always comforting to receive sound feedback. Look me up if ever on Oahu. I'd love to show you some island hospitality.
      
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  • Re: Condensation in Oil Vent Tube

    by » 9 years ago

    In Florida being humid most of the time I have only noticed the moisture you described only after ground runs never after a flight, bringing the engine up to higher power settings seems to always boil out the moisture from the oil.
    Thank you said by: Eric Nakamoto
      
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  • Re: Condensation in Oil Vent Tube

    by » 9 years ago

    I'm with Garrett on this. One of the nasty things you can do to an engine is to start it up and briefly run it on the ground. That creates an atmosphere inside the engine that is heavily laden with moisture - much of the moisture being entrained in the oil. This moisture leads to internal rust and corrosion. The best action is to fly the airplane - bring the engine's operating temperature up to at least 180 degrees for at least 30 minutes or so to boil out the water in the oil.
    Thank you said by: Eric Nakamoto
      
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  • Re: Condensation in Oil Vent Tube

    by » 9 years ago

    David,

    I know flying it is always the best to bring it to operating temp but I cannot fly it safely until April. What do you think I should do? Put it in long term storage and not warm it up at all or just warm it up on the ground for a longer period until I reach 180? I figure starting it from time to time and warming it a little is better than nothing? Thanks in advance David.
      
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