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Thread: C-85 / o-200 crankshaft seal replacement best practice?

  1. #1

    Join Date
    Oct 2018
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    C-85 / o-200 crankshaft seal replacement best practice?

    Iíve got a c-85 with some o-200 parts and need to replace the crankshaft seal again. I found a service bulliten that appears to never have been done where an angular scratch pattern parallel to the prop pitch is to be sanded into the crankshaft which I will incorporate this next time. Main question is what brand of seals are considered the best and what adhesive is considered the best?


  2. #2

    Join Date
    Jul 2010
    Elizabeth, WV
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    Is there a groove worn into the shaft by the seal lip? The Aeronca guys discussed this at length not too long ago. Advice to one who had 3 seals in a row leak was to stop about 1/8 before the seal was seated. That lets the lip ride on a fresh surface. Another tip was to cut about a 1/4 inch off the spring, making it squeeze the lip a bit tighter. The guy with the leak incorporated both tips on his last installation and has a few hours now with a dry seal.
    You can't get there from here. You have to go over yonder and start from there.

  3. #3

    Join Date
    Sep 2003
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    Brand of seals? It is probably a Chicago Rawhide part. Continental inspects it, triples the price, and puts it in a neat little bag. I have the taper shaft part # around here, but not the split one.

  4. #4
    Steve Pierce's Avatar
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    Mar 2002
    Graham, TX
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    The service instruction is one you do if you have an issue with blowing out nose seals. Usually after overhaul before cylinders get broken in. I have used aftermarket seals without any issues. Teledyne Continental Motors has a service bulletin listing the adhesive to be used. I remember using Aviation Permatex or Pliobond but that might have been on Lycomings.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers

  5. #5
    Cub Builder's Avatar
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    Mar 2011
    North Central AR
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    I don't use the split seals anymore; even on a flanged shaft.

    I remove the spring from the seal and attach it back together behind the crank flange. Submerge the seal in a cup of water and put in the microwave until it starts to boil. While it's in the microwave I apply some sealant into the pocket where the seal will be seating. Once the water boils, I let the seal steep for a minute to heat saturate. Then I stretch the seal over the crank flange. Once on the back side, it will shrink back to shape while I work the spring back into the back of the seal. Once the spring is in, I apply sealant to the outer edge of the seal and seat it in to place.

    Working the spring into the back of the seal can be challenging, but no more so than doing the same on a split seal. Stretching the seal over the flange is kind of like watching your wife give birth. Kind of hard to believe everything will shrink back to it's original shape... but it does.

    -Cub Builder
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