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Boot floor / Sub-frame / Diff mount failure thread

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  • Sorry to hear about these latest victims.

    I do wonder if this is eventually going to affect every car its just a matter of time and age.
    Ex 2001 S54
    New cars:
    Lotus Carlton
    350Z

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    • Originally posted by MGR View Post
      I do wonder if this is eventually going to affect every car its just a matter of time and age.
      There was a thread over on zroadster where someone had done the calculations and concluded that the forces under acceleration in 1st were over the fatigue limit for the components, so in that case, yes, it would just be a matter of time. I'm not sure if that related to the spot welds of the diff hanger, which also falls apart.

      Paul

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      • Hi

        I have uploaded some pictures of my trunk reinforcements....

        http://www.z3mcoupe.com/photopost/sh...00&ppuser=3588

        hope it could help someone
        ///Fredrik Larsson

        Z3M Coupe-99
        M3-88
        523iM-00

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        • Why? When BMW will replace the whole floor (with the chunkier diff clevis) for you? Resealed, repained etc...
          Imola S50 1999

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          • Originally posted by cragg711220 View Post
            Why? When BMW will replace the whole floor (with the chunkier diff clevis) for you? Resealed, repained etc...
            Will they? they don't want to touch mine!

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            • Keep pushing them, and try other dealers.
              Imola S50 1999

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              • Originally posted by cragg711220 View Post
                Why? When BMW will replace the whole floor (with the chunkier diff clevis) for you? Resealed, repained etc...
                I expect as with most things there will come a time when they won't do this. Might be better to prevent it in the long run rather than risk having pay out for the repair.
                Ex 2001 S54
                New cars:
                Lotus Carlton
                350Z

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                • Originally posted by c_w View Post
                  Will they? they don't want to touch mine!
                  if its on the road run it to cooper bmw sunderland they did mine so will have seen it before
                  id also imagine that the bmw rep will be the same so should be easier to deal with
                  [GROWING OLD IS COMPULSARY ---- GROWING UP IS OPTIONAL

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                  • Originally posted by ragerover View Post
                    if its on the road run it to cooper bmw sunderland they did mine so will have seen it before
                    id also imagine that the bmw rep will be the same so should be easier to deal with
                    It's all done now! :)

                    I probably could have pushed a bit harder but didn't want the hassle of driving all over to find sympathetics dealers, probably having the usual pay for the inspection first bit, it may or may not go through, the cars sat for weeks whilst it's arranged then further time whilst its fixed etc.

                    The first point of contact was an actual customer services name given to me from someone on zroadster who had his car fixed by BMW earlier this year. Obviously the reason I rang this person was because you would think he would be familiar with this problem, that BMW are still fixing them due to an original design defect etc, but he was just a bullshitter I was feeding him what we all know and he was not giving anything away. So BMWs initial stance is which is obvious is it's going to cost then £3/4k to do their repairs (which could be considered a bit OTT when the whole rear end of the car is removed despite the porlbem being a small location). At the same time I sent a letter to BMW head office and received a letter saying due to the age the car is no longer covered.

                    The crossmemeber part directly where the diff hanger is welded is not actually attached the to bootfloor at all and this is the cause of the problem IMO. This causes flex which then weakens and eventually breaks the welds on the bootfloor. Also the metal omn the crossmember is actually decent thickness but it's attached to a wafer-thin boot floor so that's why it tears so easily. The chassis railes running front to back on each side of the boot are where most of the strength comes from but the diff is pulling down on the centre of the cross member.

                    I've drilled out all the broken welds, and also doubled the pitch of the welds. The diff hanger is now welded directly up to the boot floor. I've also doubled up the diff hanger with a new brakcet (this is just £12 from BMW). Then a plate has been welded inside on the boot floor to cover/strengthen the whole area and welded on to the left hand chassis rail. Now I've put some sound matting back on it looks pretty much like it did originally.
                    Last edited by c_w; 31-12-2009, 11:02 AM.

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                    • chris you could go into business as a boot floor repairer

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                      • Haha nah it's a bit of a faffy job, glad it's done now!! Sheared a few driveshaft bolts which put a downer on it at the start but my dad managed to get them off; think they've been undone and tightened too many times as the diff has been changed about 4 times now. Thankfully they're only 80p each from BMW so replaced all 12 when putting it back together. And the 4 diff bolts never get easier to put in, soooo fiddly!!!

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                        • Originally posted by c_w View Post
                          And the 4 diff bolts never get easier to put in, soooo fiddly!!!
                          Think i've sworn more obsenities at those bolts than any other part of the car!!!!!!!!!
                          Black S50

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                          • Hi Guys

                            Was reading through this post the other day and thought I would go and give my car a thorough check. First here are some pics from inside the boot







                            It looks ok to me but Ive got an untrained eye. Would anyone be kind enough to have a look and see what you think?

                            Ill try and get some pictures from underneath and post those as well

                            Many thanks

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                            • It that mostly dirt or is some of it rust? I've seen quite a few Z3s with rust inside the boots which. Even with the few factured welds on mine the rust was only concentrated around those failed welds.

                              It looks "ok" but you can't really tell without removing the sound deadening (the raised bits painted blue). If you drew a line from the head of the ratchet left and vertically down from the black rubber grommet with the wireing coming out, it's that area that has 3 spot welds notorious for failing first.

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                              • You will need to take the dynomat type stuff to see the spot welds.

                                I had a split in mine which was very very slight, but the spot welds under the matting were a lot more serious.

                                It's also worth noting that BMW will not cover cars over 10 years old on a goodwill basis, they might of course take older cars on a case by case basis. But as it stands its 10 years goodwill for boot floors and only 6 years for mechanical parts (rear trailing arms/rear subframe for example).

                                BMW were more than happy to deal with it (dealer wise) and BMW CS were also very good. But i think i may have been fortunate in the sense my dealer had done a lot floor repairs (1 M Coupe, loads of e46 M3's and loads of normal e46's).

                                Thanks
                                Matt

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