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Burping the tank

in General Tech Discussion 10 years ago
Silly question but when the engine is rotated in the correct direction manually to check the oil level in the tank, why does it 'burp'?

Does it mean it is normally burping while it is running (just can't be heard due to the engine noise)?
Or is there something special what is happening when turned manually?

Sorry for silly question and thanks for the answer.

  • Re: Burping the tank

    by » 10 years ago

    It was described. It's caused because air compressed in cylinder escaping through piston rings to inside of engine and pull oil from engine back to tank. When you'll pull out oil you starts to hear this air.
      
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  • Re: Burping the tank

    by » 10 years ago

    But then why the oil pump won't bring any new oil from the tank? I suppose that by moving the prop I move the pump too. But maybe the pump is not effective enough in such a slow rotation so it won't make enough pressure to pass the oil through the filter...?
      
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  • Re: Burping the tank

    by » 10 years ago

    The pump can pull the oil out of the tank, but has no way to put it back in. The pump has no way to move the oil out of the bottom of the crankcase. So as compression gases escape past the rings it gets introduced into the bottom of the crankcase where the oil is pooling. The pressure then pushes the oil out the bottom fitting back into the oil tank.

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

    Thank you said by: Martin Horal
      
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  • Re: Burping the tank

    by » 10 years ago

    I believe the oil tank is burping continuously as the engine is running but you don't hear it. It would have to be, because the oil pooling in the crankcase must be pushed out faster than the oil coming in from the pump, otherwise the tank would go dry and the pump would pump air-disaster. The crankcase sump therefore remains dry during operation-thus a "dry sump" engine.
    Thank you said by: Martin Horal
      
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