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Thread: S50b30 swapped e34 Touring suddenly burning oil in cylinder one

  1. #1
    Join Date
    Aug 2017
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    Boulder, CO
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    My Cars
    1987 325ic 1995 525it

    S50b30 swapped e34 Touring suddenly burning oil in cylinder one

    My s50b30 from a 1995 m3, currently living in my 1995 525it converted to 5spd, is suddenly burning lots of oil under acceleration, it'll lay down a smokescreen at WOT. This condition began suddenly, the same day I recharged my AC and used the AC for the first time since I've owned it. VANOS function went from intermittent to dead about 3 days previous to the smoking and increased oil consumption. I replaced 1.5 quarts of oil over 3 months and 2k miles of mostly city driving. The engine leaks oil from the front cam seal and valve cover gasket.
    Running 5w30
    Spark plug inspection isolated oil consumption to cylinder one. Spark plug inspection 3 months ago showed a properly running motor.
    Compression in all 6 holes is 175 +/-5
    PCV breather was replaced, hoses look good.
    Repaired several vacuum leaks 3 months ago when I purchased the car and serviced it, ran great until the VANOS failed and the smoking started.
    I know the VANOS needs a rebuild - it's noisy and the engine is now showing all of the symptoms of VANOS failure.
    The car has been to an experienced BMW mechanic and I don't have a solid diagnosis for the smoke.
    No warning lights are on.

    Any ideas?

    Thanks!

  2. #2
    Join Date
    Sep 2006
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    NW suburban Chicago
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    hiss by my window
    Smoking on acceleration would usually indicate a problem with ring sealing which isn't apparent in your compression test results. Vale guides would smoke on start up and/or decel(high vacuum). You seem convinced it's not PCV related and the oil burning isolated to a single cylinder (you are sure?)convinces me to.
    I can't conceive a scenario related to the VANOS.
    If this were mine I'd be doing a leak down test beginning on #1. Sure sounds like a stuck/broken/pinched ring to me, especially given the sudden onset.
    That's all I've got
    Last edited by ross1; 04-25-2019 at 09:28 AM.

    If you can leave two black stripes from the exit of one corner to the braking zone of the next, you have enough horsepower. - Mark Donohue

  3. #3
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    1987 325ic 1995 525it
    Thanks. I just looked in the cylinders with a borescope. Every other hole looks good, cylinder 1 clearly has a drinking problem. Can't see any damage, but there's lots of carbon build up on the piston. I think the oil control ring is the problem. Trying to unstick it now, but I'm guessing this inexpensive little part is going to cost me a motor.

  4. #4
    Join Date
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    Quote Originally Posted by Bigmountianyeti View Post
    Thanks. I just looked in the cylinders with a borescope. Every other hole looks good, cylinder 1 clearly has a drinking problem. Can't see any damage, but there's lots of carbon build up on the piston. I think the oil control ring is the problem. Trying to unstick it now, but I'm guessing this inexpensive little part is going to cost me a motor.

    A good soak in Seafoam or Marvel mystery oil ought to free it up if just stuck. Fingers crossed for you

    If you can leave two black stripes from the exit of one corner to the braking zone of the next, you have enough horsepower. - Mark Donohue

  5. #5
    Join Date
    Sep 2005
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    Peoria, AZ
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    03 zhp, 97 e36m3, 04 zhp
    Or GM Piston Ring Cleaner P/N 12378549.

    It is critical in this cleaning process that the piston and ring cleaner remain in the cylinders for a minimum of two hours to fully clean the components. The cleaner solution must be removed before three hours. Additional soak time does not increase the effectiveness of this process. If solution with the dissolved deposits remains in the cylinder too long, it will soak back into the rings and cause them to stick again. If this happens, the oil economy will be reduced even further.
    Last edited by Mless5; 04-25-2019 at 12:48 PM.

  6. #6
    Join Date
    Aug 2017
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    1987 325ic 1995 525it
    The first soak with MMO made a BIG difference, I'm still in disbelief because the difference is so dramatic. It's gone from fogging out a block with thick smoke to some visible smoking at high rpm under hard acceleration at the top of the rev range. It doesn't smell like an oil fire anymore!!!

    Since carbon build up seems to be the cause of the sudden oil control ring failure, is it safe to assume that continued treatments should return the motor to the same relatively happy place it was 10 days ago?
    Last edited by Bigmountianyeti; 04-26-2019 at 05:49 PM.

  7. #7
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    2018 BMW M240i
    It won’t hurt.

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