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Thread: Oil separators

  1. #1
    Join Date
    Jan 2009
    Location
    LA, CA
    Posts
    296
    My Cars
    2000 540i,

    Oil separators

    Do they go bad? Or do they get clogged? I am replacing the CCV and oil separator hose/tube. I see some oil in intake.
    Does they oil separator drain back to oil pan? Can oil separator be flushed?
    Thanks
    1979 Chevy Camaro Z28
    2000 BMW 540i, 6speed
    2005 Chevy 2500 Duramax 4x4

  2. #2
    Join Date
    Oct 2010
    Location
    San Jose, CA
    Posts
    11,024
    My Cars
    1997 BMW 540i 6 speed
    The oil separator is mounted behind the timing chain. No history that they clog up.


    Ed in San Jose '97 540i 6 speed aspensilber over aubergine leather. Build date 3/97. Golden Gate Chapter BMW CCA Nr 62319.

  3. #3
    Join Date
    Oct 2017
    Location
    Beaverton, Oregon, USA
    Posts
    756
    My Cars
    2001 E39 540i A, 191 k
    If you remove the front covers of the engine -for a timing chain guides job ?- then you definitely want to replace the oil separator "while you are there". Otherwise, just ignore it.
    See the location of the oil separator on the M62TU engine, front covers removed
    Attached Images Attached Images
    Last edited by Chedley; 08-02-2020 at 04:51 AM.

  4. #4
    Join Date
    Nov 2016
    Location
    Charlotte, NC
    Posts
    765
    My Cars
    '02 540i-6, '97 540i-6
    These OSVs do have a history of clogging. Search this site for catch cans on M62's and you'll find plenty of owners who are did work-arounds for their clogged OSVs. I was one of them.

    There's a rubber connector at the bottom of the OSV that connects it to the a tube that drains the oil back to the sump. The bottom of the OSV is 1/4" or so wide, but the hole in the rubber connector is only 1/8" or less. That's where it can clog. I've also heard of old OSVs cracking and breaking while in the car.

    I bought an '02 540-6 a few years ago with 150,000 miles. It was burning a LOT of oil and changing the CCV didn't help. It was a waste of money -- the diaphragm in the new CCV promptly tore because the real problem was a clogged OSV. (The CCV is meant to deal with air and oil vapor, not a steady flow of oil.)

    When I was tracking down the problem and had the CCV off, I hooked a hose to the pipe under the intake that came from the OSV. When I sucked or blew on the hose, I heard the air gurgling through the oil in the OSV. It was so clogged it was acting like an oil carb -- adding oil to the CCV air flow instead of taking it out.

    I installed an external OSV and solved the problem. No more oil burning and no blown CCV.

    4 years later I had to do the chain guides. I checked and saw that the clog in the OSV was gone. That's because I'd been using variety of high-mileage (detergent) oils, AND changing the oil every 3,000 miles (even synthetic).

    In short, I think the ill-advised long oil change intervals are the #1 reason why these OSVs clog.
    Last edited by R Shaffner; 08-02-2020 at 06:09 AM.

  5. #5
    Join Date
    Nov 2016
    Location
    Charlotte, NC
    Posts
    765
    My Cars
    '02 540i-6, '97 540i-6
    Some have suggested that the OSV can be cleaned, or unclogged, by taking off the oil pan and running a wire up the tube. I tried that and it didn't work for me. I couldn't get the wire past the rubber connector to the clog.

    Others have said they tried pouring some kind of solvent down the tube under the intake. I think that has a better chance of working, but haven't tried it. Prob worth a try if you're replacing the tube anyway and think your OSV might be clogged.

    If you're just thinking about keeping it open and clean, then I suggest using high mileage oils every now and then, if not all the time, and changing the oil often.

    Also, a little oil in the bottom of the intake is normal in these engines. If it isn't a puddle and you're not burning any oil, that you notice, then your OSV is probably working OK.
    Last edited by R Shaffner; 08-02-2020 at 06:36 AM.

  6. #6
    Join Date
    Jan 2009
    Location
    LA, CA
    Posts
    296
    My Cars
    2000 540i,
    Thank you guys for the info.
    1979 Chevy Camaro Z28
    2000 BMW 540i, 6speed
    2005 Chevy 2500 Duramax 4x4

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