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Why did my exhaust gaskets live <34k miles?

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    Why did my exhaust gaskets live <34k miles?

    Talking about the gaskets between the headers and the cat section. Replaced both at 95k miles and they started leaking again before 129k.

    Any thoughts on why? If it's possibly my fault, I'd love to know so I can be more careful this time.
    2
    Install error
    50.00%
    1
    Both defective
    50.00%
    1
    These things just suck
    50.00%
    1
    2008 M3 Sedan 6MT
    Slicktop, no iDrive | Öhlins by 3DM Motorsport | Autosolutions | SPL

    2012 Mazda5 6MT
    Koni Special Active, Volvo parts

    #2
    Didn't see this was the e9x section nvm
    Last edited by Tbonem3; 10-10-2021, 09:55 AM.
    DD: /// 2011.5 Jerez/bamboo E90 M3 · DCT · Slicktop · Instagram
    /// 2004 Silvergrey M3 · Coupe · 6spd · Slicktop · zero options
    More info: https://nam3forum.com/forums/forum/m...os-supersprint

    Comment


      #3
      Originally posted by Tbonem3 View Post
      What's the cat section? Cats are in the headers on these cars.
      The primary cats are at the very front of the center section:
      Click image for larger version  Name:	RealOEM E9x M3 exhaust center section.png Views:	0 Size:	172.8 KB ID:	130978

      The gaskets in question are #3 in that pic.

      The headers themselves are just tubes.
      Last edited by IamFODI; 10-10-2021, 06:29 AM.
      2008 M3 Sedan 6MT
      Slicktop, no iDrive | Öhlins by 3DM Motorsport | Autosolutions | SPL

      2012 Mazda5 6MT
      Koni Special Active, Volvo parts

      Comment


        #4
        As long as you installed them correctly, they should not fail after 35k. What indication is there that they are leaking? TIS says to replace those self-locking nuts and torque to 27NM.

        Comment


          #5
          Originally posted by Slideways View Post
          As long as you installed them correctly, they should not fail after 35k.
          My suspicions exactly.

          Originally posted by Slideways View Post
          What indication is there that they are leaking? TIS says to replace those self-locking nuts and torque to 27NM.
          Car sounded louder than normal and sometimes ran a slightly rough. Got under it when it was cold, had someone start the engine, stuck my hands near the flanges, and felt a slight breeze around each flange.

          When I first replaced these gaskets, I definitely replaced all the hardware and I’m pretty sure I torqued everything to spec. Maybe I did a worse job than I had thought.
          Last edited by IamFODI; 10-10-2021, 10:15 AM.
          2008 M3 Sedan 6MT
          Slicktop, no iDrive | Öhlins by 3DM Motorsport | Autosolutions | SPL

          2012 Mazda5 6MT
          Koni Special Active, Volvo parts

          Comment


            #6
            Originally posted by IamFODI View Post
            My suspicions exactly.


            Car sounded louder than normal and sometimes ran a slightly rough. Got under it when it was cold, had someone start the engine, stuck my hands near the flanges, and felt a slight breeze around each flange.

            When I first replaced these gaskets, I definitely replaced all the hardware and I’m pretty sure I torqued everything to spec. Maybe I did a worse job than I had thought.
            It does not sound like it. Are both sides leaking and are these factory pipes?

            Comment


              #7
              Originally posted by Slideways View Post

              It does not sound like it. Are both sides leaking and are these factory pipes?
              Yes and yes.
              2008 M3 Sedan 6MT
              Slicktop, no iDrive | Öhlins by 3DM Motorsport | Autosolutions | SPL

              2012 Mazda5 6MT
              Koni Special Active, Volvo parts

              Comment


                #8
                Originally posted by IamFODI View Post
                I’m pretty sure I torqued everything to spec.
                First thing I'd do is check the torque. Maybe you forgot to torque them or something.

                Another possibility is that the gasket mating surfaces were not completely clean and caused a bad seal.
                2002 Topasblau M3 - Coupe - 6MT - Karbonius CSL Airbox - MSS54HP Conversion - Kassel MAP - SSV1 - HJS - PCS Tune - Beisan - MK60 Swap - ZCP Rack - Nogaros - AutoSolutions - 996 Brembos - Slon - CMP - VinceBar - Koni - Eibach - BlueBus - Journal

                2012 Alpinweiss 128i - Coupe - 6AT - Slicktop - Manual Seats - Daily - Journal

                Comment


                  #9
                  Have you removed the mid section since you installed the new gaskets? I usually consider them one time use.

                  Also I like to torque the right side first with the fixed flanged, that would pull the xpipe closer to the headers, then tighten the left side with the movable flange. I've had better luck since I started doing that.

                  Comment


                    #10
                    Originally posted by tdott View Post
                    Have you removed the mid section since you installed the new gaskets? I usually consider them one time use.
                    One-time-use is my understanding as well. I have no record or memory of pulling the cat section since installing the gaskets.

                    I did have to pull the muffler section for something fairly recently. Maybe we didn't quite support the cat section enough and ended up tweaking the flanges at the headers or something? That's all I got.


                    Originally posted by tdott View Post
                    Also I like to torque the right side first with the fixed flanged, that would pull the xpipe closer to the headers, then tighten the left side with the movable flange. I've had better luck since I started doing that.
                    Nice. Thanks for the tip.
                    2008 M3 Sedan 6MT
                    Slicktop, no iDrive | Öhlins by 3DM Motorsport | Autosolutions | SPL

                    2012 Mazda5 6MT
                    Koni Special Active, Volvo parts

                    Comment


                      #11
                      Always replace the hardware with those donut gaskets. At least replace the lock nuts. If you tighten the fasteners improperly, you'll get a hot spot on the gasket and it will blow out a section of the gasket. Then the gasket just comes apart.

                      Comment


                        #12
                        Originally posted by bigjae46 View Post
                        Always replace the hardware with those donut gaskets. At least replace the lock nuts. If you tighten the fasteners improperly, you'll get a hot spot on the gasket and it will blow out a section of the gasket. Then the gasket just comes apart.
                        A-ha. There’s a plausible hypothesis.

                        I did use new fasteners and thought I had torqued them to spec, but I guess it’s worth a second look. Thanks for weighing in.
                        2008 M3 Sedan 6MT
                        Slicktop, no iDrive | Öhlins by 3DM Motorsport | Autosolutions | SPL

                        2012 Mazda5 6MT
                        Koni Special Active, Volvo parts

                        Comment


                          #13
                          FWIW: turns out my engine mounts were shot and there were holes in the exhaust between the primary and secondary cats. We think the excess engine movement plus year-round-DD-in-the-northeast rust might have accelerated the failures, and I wrongly attributed (most of) the excess exhaust leaks to the donut gaskets.
                          2008 M3 Sedan 6MT
                          Slicktop, no iDrive | Öhlins by 3DM Motorsport | Autosolutions | SPL

                          2012 Mazda5 6MT
                          Koni Special Active, Volvo parts

                          Comment

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