m20b27 using a little oil, knocking at idle

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  • jstam
    Member
    • Jul 2010
    • 48
    #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
    • MR 325
      Moderator
      • Oct 2003
      • 37827
      #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

        Comment

        • riceh8r
          Advanced Member
          • Dec 2010
          • 133
          #3
          Amen

            Comment

            • lateracer
              Grease Monkey
              • Sep 2009
              • 302
              #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

                Comment

                • jstam
                  Member
                  • Jul 2010
                  • 48
                  #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

                    • TrippinBimmer
                      Advanced Member
                      • Feb 2011
                      • 182
                      #6
                      Maybe a Cam seal...:(

                        Comment

                        • MR 325
                          Moderator
                          • Oct 2003
                          • 37827
                          #7
                          Originally posted by jstam
                          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

                            • matt0300
                              E30 Addict
                              • Mar 2011
                              • 549
                              #8
                              I mean Mobil 15w40 synthetic works just as well

                                Comment

                                • matt0300
                                  E30 Addict
                                  • Mar 2011
                                  • 549
                                  #9
                                  Look at valve stem seals and do a valve adjustment.

                                    Comment

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