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Thread: CC-340 Crankcase oil seal

  1. #1
    Junior Member
    Join Date
    Jan 2014
    East Lansing, MI

    Default CC-340 Crankcase oil seal

    Has anyone had problems with the Crankcase Oil Seal on a CC 340? The engine has 100 hours and a balanced prop. Thereís oil up on the front of the cowl and front engine parts but Iím not sure itís from the oil seal. I checked all the usual suspects but no signs of a leak. It seems odd that the seal would start to fail after only 100 hours. Iím curious if anyone else has had this issue before I pull the prop, put in a new seal, etc.

  2. #2
    Senior Member Andy's Avatar
    Join Date
    Dec 2019
    Glendale, AZ

    Default Re: CC-340 Crankcase oil seal

    When I received my FX-3 I was cautioned that the crankcase breather tube in the exhaust system must be kept clear. Does your engine have this breather arrangement? If so, have you kept it clear?

  3. #3
    Senior Member
    Join Date
    Mar 2016

    Default Re: CC-340 Crankcase oil seal

    As Andy has stated, the exhaust breather tube requires cleaning about every 100 hrs (EX-2). If this gets plugged, then you can see increase crankcase pressures and possibly oil blow by at the seals.

    I don't know about the FX-3 configuration, but on the EX-2 it is easy to clean. I use a rifle bore brush cleaning rod with a 45 cal brush on the end, use a small battery powered drill to clean it out. Look up the exhaust stack and right in the middle is the breather outlet.

    Let us know what you find out as the front seal should go longer than 100hrs as you know.
    Last edited by aeroaddict; 10-05-2020 at 08:14 AM.
    Dan Arnold

  4. #4
    Senior Member 40m's Avatar
    Join Date
    Sep 2013
    Shoreham, VT

    Default Re: CC-340 Crankcase oil seal

    Technical Publications
    SI0023 Breather Tube
    Last edited by 40m; 10-05-2020 at 12:54 PM.

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