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Clacking sound at idle after VANOS/rod bearings

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    #1

    Clacking sound at idle after VANOS/rod bearings

    Hey guys, looking for some help here. Got things put back together yesterday after some major work that included a vanos overhaul as well as rod bearing change, and generally a major refresh. Things seemed to startup fine but I can hear a tapping sound at idle and I'm not sure what it is. I uploaded a video here where you can hear it both while idling and as I rev the engine a bit: https://youtu.be/SpToi1alavk

    I've looked at both the oil filter and vanos filter and there doesn't appear to be any metal in either, and the oil I drained looked very clean. I recorded all my bearing clearances and angle torques in a spreadsheet when I did the bearings and everything looked good there, so I'm really hoping there's nothing wrong with the bearings. I replaced all the major "while you're in theres" including cam bolts, timing chain guide, tensioner, as well as any gaskets I could get to.

    I did a valve adjustment also and there was one intake valve very far out of spec (I took out a 2.22mm shim and put in a 2.48mm shim), while most of the rest of the valves that needed changing only need 0.04mm of adjustment. The only other thing I can think of that would cause a noise like that is the chain hitting somewhere.

    I'm going to pull the valve cover and re-check all the clearances, and then next would be to pull the oil pan and make sure all of the rods look like they should. Any other ideas of what's making this noise? Thanks.
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    #2
    A valve is out of spec or a shim popped out.

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      #3
      Originally posted by Slideways View Post
      A valve is out of spec or a shim popped out.
      I just went and re-checked all of them. A number of valves that I had measured as being loose originally now felt too tight, so I re-adjusted to the appropriate clearances. Hopefully that fixes it.

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        #4
        https://youtu.be/8cjs3lwoueI


        This is after adjusting the valves. I can still hear it when I'm in the engine bay but not so much from the driver's seat. I honestly can't tell if this is normal or not for this engine as it's been a while since I've had it running.

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          #5
          Is it possible it made this sound before and you're only now hearing it because you're paying attention?

          Could it be the fan clutch or a pulley?

          I would move around with a screwdriver as stethoscope and try to narrow down the source of the sound.

          • Likes 1

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            #6
            Originally posted by cobra View Post
            Is it possible it made this sound before and you're only now hearing it because you're paying attention?

            Could it be the fan clutch or a pulley?

            I would move around with a screwdriver as stethoscope and try to narrow down the source of the sound.
            I pretty much bought the car, drove it 1200 miles home, and then started disassembling it to swap parts over from my previous m3 to sell and then get started with the overhaul. All the pulleys and the fan clutch are new OE.

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              #7
              Originally posted by DoubleSidedTape View Post

              I pretty much bought the car, drove it 1200 miles home, and then started disassembling it to swap parts over from my previous m3 to sell and then get started with the overhaul. All the pulleys and the fan clutch are new OE.
              I counted the ticks and there were 84 in 10 seconds, so 504/min. Hope that helps narrow it down.
              • Likes 3

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                #8
                It seemed to be loudest when I put the screwdriver on the injectors. On the metal of the vanos or the head I mostly can hear a wooshing sound but the tapping is very clear with I touched the injectors. I could only really get to the front two.

                I had the injectors cleaned when the engine was apart and everything seemed ok.

                Got the car up to temp, it seems to rev nicely, still too cold and snowy here to drive it around, but I am gonna at least rinse the car off from all the dust and metal bits that have been flying around the garage for the last few months.

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                  #9
                  Originally posted by cobra View Post

                  I counted the ticks and there were 84 in 10 seconds, so 504/min. Hope that helps narrow it down.
                  That's some forensic investigation Joo-Joo right there!
                  Build thread: Topaz Blue to Shark Blue​
                  • Likes 1

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                    #10
                    Originally posted by DoubleSidedTape View Post

                    I just went and re-checked all of them. A number of valves that I had measured as being loose originally now felt too tight, so I re-adjusted to the appropriate clearances. Hopefully that fixes it.
                    Another person with a supercharged track car had this same noise after retiming the engine and he ended up bending a pair of valves. The tapping sound would become much more noticeable as the engine started warming up. Hopefully that is not the case, but you already ruled out the valve adjustment.

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                      #11
                      This is what it would sound like if you had a loose rod cap after replacing rod bearings:

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