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Unknown Chip in Engine Oil...Yikes!

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    Unknown Chip in Engine Oil...Yikes!

    When changing the oil in my 1992 318ic yesterday, I noticed a couple of small chips in the old oil. On close inspection, I determined (with a magnet) that they were not ferrous, and they appear to be a brittle plastic of some sort. Of course, they could also be aluminum, but I don't know if there are any internal aluminum components in the M42. Although I have 130K miles on the engine, I take very good care of it, and it operates, sounds, and feels great. I suspect this chip might be a piece of a gasket or internal seal, but I haven't seen or heard any evidence of engine problems, and there didn't appear to be any more chips in the oil filter either. This one has me stumped and a little concerned...any ideas what it might be?

    #2
    Looks like part of a timing guide, I'd bet one below the crank sprocket has fallen apart.

    Don't worry if that's the case as that guide is basically superfluous, but you should pull the valve cover to look down at the upper guides.

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      #3
      Thanks, Rogue...that makes sense, and at least gets me pointed in the right direction. One question, though...assuming this has been going on for some time, what's the risk of not pulling the valve cover and checking the upper guides?
      Last edited by flyer92; 10-24-2020, 06:26 PM.

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        #4
        Likely not much as the other guides are fairly robust, but you should know that the crank sprocket (which has a plastic inner section) is the thing that would fail and cause the pistons to eat valves. IMO, pull the VC and look, it takes a maximum of 20 minutes, and a few bucks for a new gasket.

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          #5
          OK, thanks again...will definitely check it out soon. Much appreciated!

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            #6
            I’ve been wondering about a metal piece found 5 years ago on my magnetic oil drain plug
            1991 318is, AWII, Eibach/GC, Koni
            Riverside CA

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              #7
              1991 318is, AWII, Eibach/GC, Koni
              Riverside CA

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                #8
                A couple more pictures
                Attached Files
                1991 318is, AWII, Eibach/GC, Koni
                Riverside CA

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                  #9
                  That is definitely a piece of timing chain roller. Have you replaced the timing chain, tensioner and guides since you found the piece? If not, then you are due for a timing overhaul. Also, you really need to drop the lower oil pan and do some checking. It is entirely possible that other chunks got pulled up into the pickup and are sitting against the filter screen. As I and a number of others discovered, those metal bits can get pulled through the screen and explode the oil pump, leading to a total replacement of the timing case (assuming you don't cook the engine from loss of oil pressure first). The other thing you need to do is check that the bolts that hold the upper pan to the timing case are all still in place and tight. They have been known to work themselves loose and fall out, leading to one of the gaskets at the pickup imploding and running air into the lubrication system. They can only be checked with the lower pan off. If loose, spray out the threads on the bolts and holes with some brake cleaner and then reinstall them with some thread locker.

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