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Thread: Harrison oil cooler

  1. #21
    Gilbert Pierce's Avatar
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    Default Re: Harrison oil cooler

    I have had a leaking propseal that deposited oil in the same places shown in your picture. The back side of the flywheel was dry. In desperation I pulled the prop and flywheel and found the seal wet. The oil was following the case split line and then dripping on the starter and exhaust crossover. Replacing the prop seal dried up the engine.

  2. #22

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    Default Re: Harrison oil cooler

    Thank you, Steve & dgapilot.

    Does oil flow to the oil cooler only above some set point temperature? Somewhere between 140F and 160F?
    [I am trying to rule out leaks from the engine block, which remains free from oil until that temp range.]

    How may turns past finger tight should I (dare I) thread the NPT thread of the aluminum AN fitting into the aluminum thread in the oil cooler?

    Thank you.
    Vas

  3. #23

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    Default Re: Harrison oil cooler

    Thank you, Mr Pierce. I just saw your post. I was hoping this was not it.
    Is it possible that prop seal leak would only present at higher oil temperatures/pressures?
    The oil pressure comes up from 40 psi to 80 psi as the temperature rises from 100F to 140F.

    Thank you,
    Vas

  4. #24
    Gilbert Pierce's Avatar
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    Default Re: Harrison oil cooler

    I would guess as the oil heats up thins out it probably is more likely to get past the oil seal. Any unusual crankcase pressure will exacerbate the problem caused by excessive blowby or inadequate crankcase vent.

  5. #25
    Administrator Steve Pierce's Avatar
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    Default Re: Harrison oil cooler

    Quote Originally Posted by vas View Post
    Thank you, Steve & dgapilot.

    Does oil flow to the oil cooler only above some set point temperature? Somewhere between 140F and 160F?
    [I am trying to rule out leaks from the engine block, which remains free from oil until that temp range.]

    How may turns past finger tight should I (dare I) thread the NPT thread of the aluminum AN fitting into the aluminum thread in the oil cooler?

    Thank you.
    Vas
    With either a Vernatherm or a viscosity valve the oil won't run through the cooler until it warms up.

    As far as fittings go I tighten them till tight where the oil line isn't going to loosen it.

  6. #26
    Vagabondblues's Avatar
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    Default Re: Harrison oil cooler

    Quote Originally Posted by vas View Post

    How may turns past finger tight should I (dare I) thread the NPT thread of the aluminum AN fitting into the aluminum thread in the oil cooler?

    Thank you.
    Vas
    Parker Hannifin has a publication for their aerospace tubing/piping products, which is the 4300 catalog. In chapter seven of the catalog they address the tightening of NPT threads. Parker Hannifin uses a formula based on the diameter of the thread and T.T.F.T. (Total Turns from Finger Tight).

  7. #27

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    Default Re: Harrison oil cooler

    Thanks to all.

    After several clean and run cycles I found that the leak is either the nose seal or the crank case seam just below the oil seal. The oil runs down and aft along the seam, then forms droplets on the starter motor bolt heads, which drops then drip down onto the oil cooler. This continues for a short time after shutdown.

    I decided to replace and properly torque the two AN6-34A crankcase through bolts, and also to replace the nose seal.
    The bolts and solid lw-13792 seal for O-320 (no suffix) lycoming arrived yesterday and here I am with parts and tools and solvent and pliobond at the hangar today.

    Cripes. The installed seal is sl-76940-e, which is described as a split seal for O-235 & O-290, without the molded lip.

    Now I am afraid to pull the 76940 for fear of finding no groove in the shaft bore for the molded lip of the lw-13972 replacement. Plus I see no solid replacement for split 76940. Does this mean the only way to replace it is a tear down?

    At least I can replace the bolts while I am here.. Is there a proper procedure for that?

    Please advise.

  8. #28
    Administrator Steve Pierce's Avatar
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    Default Re: Harrison oil cooler

    Probably need an 76940 which is a split seal which they call out if you have the retaining plate. If no retaining plate the LW-13792 is a solid type and can be done without the tool, i carefully used a small pry bar. I can loan you the tool if you like. Follow this Service Instruction.

    https://www.lycoming.com/sites/defau...il%20Seals.pdf

  9. #29

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    Default Re: Harrison oil cooler

    Thank you, Steve.

    There is no seal retaining plate, nor the threaded holes for the plate mounting bolts. I interpret your response to mean that the existing 76940 seal should not have been used, and that I can expect the crankcase bore to have the groove for the molded lip on the 13792 solid replacement, shown as a tiny ‘v’ in the cutaway diagrams (fig 2) in the service bulletin you cited.

    Correct?

    Vas
    Last edited by vas; 03-31-2018 at 10:47 AM.

  10. #30
    Administrator Steve Pierce's Avatar
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    Default Re: Harrison oil cooler

    I don't remember seeing a groove in the bore. The info came from my O-320 parts manual.

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