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Thread: External Oil Filter Siphoning into Crankcase? 1960FL

  1. #1
    Join Date
    Nov 2015
    Posts
    14

    Default External Oil Filter Siphoning into Crankcase? 1960FL

    I just spent several weeks getting a good seat on a cast iron oil pump’s check valve. What ultimately worked for me was a 3/8” ball, fine, double fluted burr mill followed by a LIGHT touch of burnishing followed by lapping with a 3/8” ball and some very fine compound. After many attempts of various approaches, this sealed it.....on the bench. I plan to run it later this week and then wait to see what happens.

    However, in the process of putting it back together, I got to wondering if the scavanger line from the oil pump to the external oil filter could possibly siphon oil out of the oil filter canister back into the crankcase? There’s a check valve in the top of the OEM filter housing. Is this meant to be sufficient to prevent siphoning? I have seen a lot here about check valve siphoning but can’t find mention of siphoning from the oil filter canister back into the crankcase. Is it possible? Has anyone experienced this?

    Any insight or shared experiences with this is appreciated.

    Brad

  2. #2
    Join Date
    Jan 2005
    Location
    Vancouver Island B.C.
    Posts
    435

    Default

    Never heard of one siphoning back. The check valve in the top is to bypass the filter if it gets to plugged so the engine doesn't get starved of oil.

  3. #3
    Join Date
    Aug 2004
    Location
    Beautiful Northern New Mexico
    Posts
    2,353

    Default

    The outlet line for the filter exits into the vented area of the oil tank, so there is never a chance of vacuum being created in the filter housing, therefore never a chance to siphon.
    Robbie Knight Amca #2736

  4. #4
    Join Date
    Nov 2015
    Posts
    14

    Default Thanks for the replies and pic of burr mill

    This is good news....I have enough problems without dreaming up non-existent ones! Thanks for the help!

    By the way, below is a pic of the 3/8” burr (not ball mill) I used to face my check valve seat. I purchased it from MSC. It’s called “double cut” and/or “diamond cut”. I also recall it using the word “fine”. I used only hand pressure and maybe five revolutions.....followed by a light burnishing and lapping. A special thanks to Steve LeMay - Resurrection Cycles - for his help with this.

    FC541B62-4EEE-4232-B651-EA581DCDCCEB.jpg

    Brad

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