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Thread: Lycoming oil suction tube problem

  1. #1

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    Lycoming oil suction tube problem

    On the A and B series engines the Oil Suction Screen goes into sump from the bottom of the engine and is captured by p/n 61381 suction tube. Have any of you amazing mechs out there had any problems with this brazed assembly, specifically, it sucking air at the gasket where it mounts inside the accessory case? I have an engine that suddenly developed a problem at a normal oil change (also cleaned screen). Won't make over 25 psi oil pressure. It also has an AirWolf remote filter kit which has been trouble free for years. No metal in oil and Airwolf guys said I might have a bad spin-on filter, but tried another to no avail. First, I did put a calibrated gage and hose on it to verify its not a gage problem. Anyone have any ideas before I remove the Sump? Hoping someone has seen this.

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    Gordon Misch's Avatar
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    A bit of crud under the oil pressure relief ball?
    Gordon

    N4328M KTDO
    My SPOT: tinyurl.com/N4328M (case sensitive)
    Likes ak49flyer, Steve Pierce, DENNY liked this post

  3. #3

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    Never seen the gasket or tube assy leak but have seen Gordon’s scenario multiple times.

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    www.SkupTech.com mike mcs repair's Avatar
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    hose flapper in hose end assembly....

  5. #5
    skywagon8a's Avatar
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    Quote Originally Posted by Gordon Misch View Post
    A bit of crud under the oil pressure relief ball?
    Just one small piece will do this when it sits between the ball and the seat.
    N1PA

  6. #6

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    I don't really post here, just sneak in and read for education but in over 40 years as an AP/IA I have had 3 experiences with this. Normal oil change and a tiny bit of crap gets disturbed and contaminates the relief valve. Good on you for checking the suction screen, so many don't do it. The really frustrating part is that many times I have not actually found the bit in the ball/seat, just fixed the problem by "looking". That's where I would start and the good part is that is an external item, go deeper only as a last resort.
    I've had far too many cases of target fixation that took good techs down the rabbit hole and pulled me right in after them.
    Ken

  7. #7

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    It changed after an oil change? I’d retrace my steps. Filter already swapped. When you say you cleaned the screen do you mean the suction screen? Have you removed and double checked that?

    When you tried a different gauge did you use the same restrictor fitting? It’s easy to imagine that getting fouled.

  8. #8

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    Quote Originally Posted by Gordon Misch View Post
    A bit of crud under the oil pressure relief ball?
    Yes, I'm hoping for this one! I did buy a new ball and spring and they are ready for install with the crush washer. Thanks so much, guys! I will let you know when i get back in town to get it done. --DRB

  9. #9

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    Thats a great thought too. The external gage is still on there so after I check the ball and seat, if no luck, then i will send a soft wire through the fitting --or maybe compressed air..... or maybe remove it first, lol.

  10. #10
    skywagon8a's Avatar
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    Quote Originally Posted by Tunria View Post
    Yes, I'm hoping for this one! I did buy a new ball and spring and they are ready for install with the crush washer. Thanks so much, guys! I will let you know when i get back in town to get it done. --DRB
    It may just be a spec of carbon between the ball and seat. Not likely to need to replace the ball & spring.
    N1PA

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