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    Engine clicking

    Hey guys i have a M42b25 in my E30. on idle it clicks pretty aggressively and its a little worry some. also not sure if its to do with the same issue but when im driving at 2100 rmp it makes a weird grin sound... mainly just on hills now.

    #2
    M42b25?? Impossible

    Sent from my Pixel 3 using Tapatalk
    '91 318i (Alpine) - daily
    '88 325ix (Zinno) - drive here and there!

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      #3
      2100 rmp it makes a weird grin sound
      Isn't it RCMP in Canada?

      That weird grin sound might just be the timing chain working on your chain case.

      Or the tensioner sprocket, having shed its bearing bits, now acting as a slider...

      and yes, you most likely have an M42b18. Unless someone built you a VERY special motor...

      So yeah, best to investigate. A mechanic's stethoscope is $12CDN, and really makes
      this a lot easier. I find it a lot more accurate than the big screwdriver trick.
      Then when you find WHERE exactly the noise is coming from, you'll know more.

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

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        #4
        Originally posted by TobyB View Post
        Isn't it RCMP in Canada?

        That weird grin sound might just be the timing chain working on your chain case.

        Or the tensioner sprocket, having shed its bearing bits, now acting as a slider...

        and yes, you most likely have an M42b18. Unless someone built you a VERY special motor...

        So yeah, best to investigate. A mechanic's stethoscope is $12CDN, and really makes
        this a lot easier. I find it a lot more accurate than the big screwdriver trick.
        Then when you find WHERE exactly the noise is coming from, you'll know more.

        t

        No RPM. RCMP is our police. my buddy told me it was that engine. all i knew was slanted 6 lol

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          #5
          Originally posted by fresh_TD View Post
          M42b25?? Impossible

          Sent from my Pixel 3 using Tapatalk

          How so?

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            #6
            The M42 is a 1.8 liter 4 cylinder. As far as we know, it's only been stroked to
            2 liters, not 2.5, and it's not crank- compatible with any longer- stroke cranks out there.

            Are you sure you have an M42? M20B25 is very common in E30's, but it's a 6 cylinder.

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

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              #7
              You can get the M42 out to 2092CC. Bore to 87mm, and swap in an 88mm stroke M47 crank (which requires a little machining to make the nose work with the M42 timing chain sprocket and damper). I think that someone found another crank with 91mm stroke whigh would fit with more extensive machining, but I have not seen any running builds with it. Going past an 87mm bore isn't a hot plan since the cylinder pitch is only 91mm.

              Anyway, grinding noises from the M42 usually indicate timing case issues. Letting those go for too long usually means a dead engine. Without more detailed info, there's not much we can suggest.

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                #8
                I'm banking that this guy has an M20 with clacky valves and maybe a cracked rocker.

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                  #9
                  Ok i figured out its not the engine i had said. the clicking sounds like something metal hitting another metal thing.. if that helps??

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                    #10
                    oh my god that is insanely helpful

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                      #11
                      I vote for a little man with a hammer in his left bypass tube...

                      OP, figure out which engine you have,
                      and then change your timing belt and lash your valves.

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

                      Comment


                        #12
                        Here's an easy way to find out what engine you have (if its never been swapped)...

                        ...is your car a 318 or 325?

                        Once we have this MOST BASIC of information, we can further start to help you figure out if its a little man with a hammer or not.
                        Steve Toronto
                        1991 318is Brillantrot
                        Build Thread

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                          #13
                          OP forgot to let his trunk monkey out.

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