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  • Strange little noise...

    Chaps,i can hear a slight noise when coming down the rev's around 25k mark and only when reducing power,its not from the engine/vanos but near the drivers seat underneath,bracket/cats/ ?? its only a light sound,no loss of power going up the revs at all,any pointers? TIA.

  • #2
    Try wobbling the exhaust, if it makes the same noise chances are one of the brackets that secure the front pipe has corroded through.

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    • #3
      Several parts under the drivers seats so worth checking the exhaust mounting and protective shield also mounting for large undertray is in that area

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      • #4
        Hope your not Erving to 25k
        If so you have an issue
        If you mean 2.5 k
        Chances are it's a heat shield
        If I remember correctly the cats mount just next to drivers seat
        [GROWING OLD IS COMPULSARY ---- GROWING UP IS OPTIONAL

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        • #5
          Just seems strange that its when coming the revs...

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          • #6
            Originally posted by kwoffa View Post
            Just seems strange that its when coming the revs...

            That's probably just the point when the correct resonance kicks in to set it off
            2002 '52 S54 - Titanium Silver with 18" BBS LMs, AP Racing BBK, KW V3, H&R anti roll bars & ACS flippers (previously 2000 'X' S50 - Arctic Silver)

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            • #7
              I will get underneath and have looksie .

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              • #8
                Is it worth checking the cats themselves ?

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                • #9
                  Every time (twice) when I have had the same type of noise coming beneath the car with certain revs it has been the front exhaust support bracket : part nbr 9 in this schematic : http://bmwfans.info/parts-catalog/Z3..._lambda_probe/

                  It had a minor amount of corrosion but had been neatly broken into two parts and the broken ends were rubbing against each other due to vibration. It was not very obvious to notice but only noticed it after trying to wiggle the exhaust from side to side and noticed that the bracket is actually not holding.

                  Perhaps this was due to vibrations or overtightening or something else. Nowadays this is the first thing for me to check if there is some resonance noise coming beneath the car. The sound travels nicely through the exhaust system so it can seem to come from front or back given the situation.
                  The older I get, the faster I was ...
                  BMW HP2 Sport
                  ex- BMW Z3 M Coupe - Cosmosschwartz Metallic

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                  • #10
                    Juhav...
                    Your absolutely right mate,from underneath i could see it almost looks twisted but not attached! mant thanks.

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                    • #11
                      I got a very similar noise at 2.5k

                      Thanks for this

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                      • #12
                        The older I get, the faster I was ...
                        BMW HP2 Sport
                        ex- BMW Z3 M Coupe - Cosmosschwartz Metallic

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                        • #13
                          New bracket's installed,No more rattle.. Cheers chaps.

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