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m20b27 using a little oil, knocking at idle

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    #1

    m20b27 using a little oil, knocking at idle

    I was under the e30 this weekend draining coolant and replacing a hose, and noticed that there is new oil on the block. Doesn't drip, just some oil on the front half of the block. This I suppose is the source of the slow oil consumption that i've been seeing (1qt down after a couple of track days). The motor also is knocking at idle, but seems to improve after warmup.

    All else is normal - no smoke, coolant didn't have visible oil in it (although there is some sludge in the bottom of the expan. tank), oil was in OK condition last time it was changed (didn't send to blackstone, but will send next one though).

    I'm sure this could be a range of problems, but to diagnose this I'm thinking I need to run a compression test. Any ideas what else I should look into? As the sig states, this is a pretty low mileage engine, and it has never been opened up.
    1985 325e, 74k miles (S52 w/ OBD1, Bistein Sports, H&R Sports, IE sways, 3.23 LSD, TD 15x7/Star Specs, Euro bumper conversion)
    1998 M3 (4dr, 5sp, TCKline) (sold)
    2002 325i (sold)
    2009 X5 3.0si
    Tags: None
    #2
    Just curious, what oil are you using? Should be running 20w50 if you're not.
    BimmerHeads
    Classic BMW Specialists
    Santa Clarita, CA
    www.BimmerHeads.com

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      #3
      Amen

      Comment

        #4
        A little sludge in the coolant from the deep recesses of somewhere in the system is common for a car that's getting tracked. I chemical flushed my coolant system and cycled it through a few heat cycles and clean water drain/fills. Stayed clear during reasonably civil highway runs and some in town driving. After three hours of track use, it was brown.

        See what the blackstone analysis says. Do a compression test or a leak down if you have the time. Hope that it's not a rod knock. Even if it is, it can probably be fixed without pulling the motor.

        Can you tell where the oil is leaking from?
        sigpic

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          #5
          20W50 Castrol GTX, always has been. Not to get into another oil discussion, but another forum has guys saying I should run 0w40. Seems like I'd really have a leak then...

          Re. location of leak, it seems to be the front right of the block at the head gasket. Hard to tell exactly though.
          1985 325e, 74k miles (S52 w/ OBD1, Bistein Sports, H&R Sports, IE sways, 3.23 LSD, TD 15x7/Star Specs, Euro bumper conversion)
          1998 M3 (4dr, 5sp, TCKline) (sold)
          2002 325i (sold)
          2009 X5 3.0si

          Comment

            #6
            Maybe a Cam seal...:(

            Comment

              #7
              Originally posted by jstam View Post
              20W50 Castrol GTX, always has been. Not to get into another oil discussion, but another forum has guys saying I should run 0w40. Seems like I'd really have a leak then...
              Definitely no not listen to them! The factory called for 20w50 in the M20 engine.
              BimmerHeads
              Classic BMW Specialists
              Santa Clarita, CA
              www.BimmerHeads.com

              Comment

                #8
                I mean Mobil 15w40 synthetic works just as well

                Comment

                  #9
                  Look at valve stem seals and do a valve adjustment.

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