Main bearing #3 toast?

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  • arrayxt
    Noobie
    • Oct 2019
    • 18

    #1

    Main bearing #3 toast?

    As I continue refreshing my M42, I got to taking my upper oil pan off to get a quick look at the general condition of the bottom end. I unfortunately saw what looks to be pieces of bearing that may have broken off on the center main bearing, however I'm not 100% sure. Here's a picture:

    Click image for larger version  Name:	P_20191216_204608_004.jpg Views:	0 Size:	74.8 KB ID:	9892599

    So the question is, should I be looking into getting new main bearings? Or am I just being paranoid? (I sure don't think so)
    I don't want to have to take the bottom end apart if I don't have to, but I will fix what needs to be fixed to get this motor running reliably. The oil I drained from the motor didn't look shiny or metallic, and I could only find what seemed to be very tiny chunks of the timing chain guides, nothing I believe to be a cause for concern, but I may be wrong. The majority of the timing chain system looks to be in decent shape, however it definitely needs a new tensioner.
  • e30davie
    E30 Mastermind
    • Apr 2016
    • 1788

    #2
    Pull that cap off and take another photo.

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    • arrayxt
      Noobie
      • Oct 2019
      • 18

      #3
      I'll get a picture of it tomorrow. Do I need a torque wrench to get that cap back on and can I reuse the bolts? I don't have a lot of tools with me at the moment.

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      • roguetoaster
        R3V OG
        • Jan 2012
        • 7753

        #4
        You absolutely want a torque wrench to reassemble. Bolts are okay to reuse.

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        • arrayxt
          Noobie
          • Oct 2019
          • 18

          #5
          Click image for larger version  Name:	image_146849.jpg Views:	4 Size:	96.1 KB ID:	9892752 Click image for larger version  Name:	image_146850.jpg Views:	4 Size:	74.3 KB ID:	9892753
          Definitely some good damage there, not quite sure why this would happen. I pulled the other caps off as well and all the other bearings looked to be in decent shape, minus a few small marks here and there.

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          • roguetoaster
            R3V OG
            • Jan 2012
            • 7753

            #6
            Not an expert, but that has to be contaminant damage or a blocked galley as the upper is okay. Excellent spot when you pulled the pan BTW!

            Comment

            • TobyB
              R3V Elite
              • Oct 2011
              • 5169

              #7
              Or oil starvation...

              The bearing is done, the crank might polish- BMW mains are hellaciously stout.

              Given how that looks, tho, time to look at all the rod bearings. #3 is the canary in this coal mine...

              t
              now, sometimes I just mess with people. It's more entertaining that way. george graves

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