'You are right that there appears to be less acknowledgement of the problem in other countries compared to the UK'

Probably because our roads are so crap!

I've heard a few people mention recently that they think its the bushes that are causing the cracks. That could be true of the crack at the front right rear subframe bush, but what about the cracked seam in the lower inner arch? Or the floor pan at the front of the spare wheel well area? I dont think so personally.

I've used both the Turner motorsport repair kit, & the Reddish Motorsport kit. Reddish one a lot better. There is also the option of cutting open the chassis inside the car, just behind the rear seats. The spot welds are then visible which split, so these are welded. Unfortunately you do end up with a couple of welded plates in the boot, only visible if you lift the carpet.

Sorry Alex, been very busy today and not had an M3 in. I may have some endoscope shots saved at work, I'll see if I can find them tomorrow.

Hi James,

No problem, thank you again for your help! :)

I'm not really in a hurry, I was just wondering what I could do as a preventive work as this spoils the pleasure of ownership a bit.

So before I make an irreparable mistake, like selling the CSL during the winter, I was wondering what I could do.

Kind regards,
Alex

Hi,

Quote- '''You are right that there appears to be less acknowledgement of the problem in other countries compared to the UK'

Perculiar statement given that it was a
Multipile Class Action by owners in the
States that kicked this all off.

The problem is a piss poor design made worse
by the fact that even the BMW remeadies are
aimed at recitfying the symptoms not the
cause.

I would not be at all surprised to see some
of the BMW ''fixes'' starting to unravel in
a few more years, maybe sooner.

The 10 year window has fuck all to do with fixing it,
its BMW's way of saying, your car, your fucking problem,
were now all done on that.

Who ever thought that mounting a load bearing
torque absorbing rear subframe, itself subjected
to high loads and lateral forces, on four mount
points all on the same plane without any chassis dowels
into the securing bushes was a clever design, should never be allowed
to design anything again, but to compound the issue by
elongating one of the bush holes to facilatate
subframe fixing, instead of moving complant bushes,
to facilitate bolt fixing and assist with absorbing
load, they should be shot.

Christ even Merc 190's have chassis dowels fitting into the
rear subframe bush to prevent 'sawing' stresses ripping
at the mount points and surrounding sheet etc.
All the laod and movement is absorbed by the bush,
the bush wear out and are replaced, BUT the mounting
points never move !!!
They were designed in 1983 and BMW has just
started to emulate that design in the E90 series etc.

As for ripping out distorted boot floors and re-welding
in new ones, well ye olde Roost monster will be having
a field day, even more so with anything synthetic filling
the boot floor skin voids, as any fucking retard knows
that when a cold surface, the boot floor skin meets a warm surface,
the expoxy filler or whatever, then hey presto, its called condensation and
guess what its water, and water on internally welded metal makes for
a loverly feeding ground for the Roost monster.

And they reckon I am on drugs, fuck me, well at least mine
in part are working some.

The fact remains the E46 Rear subframe fixing design
is kinder garten design at its very worst, its nothing to
do with the boot floor not being strong enough, or
to many launches in this gear or that gear, its the
very basic fact that any rear subframe should have
securing dowels as part of the chassis that fit into the
bushes on the subframe, or the back rear Bushes should
have been on a different plane to the front ones in
the very least, to counter any subframe movement which ideally should
be absorbed by the bush not by the the 4 H/T bolts ripping
at the sheet metal ala the BMW design, made worse
by the elongated hole.

But hey as the AD says ''Joy''.

Regards,

The Gorilla.

Danny,
Do you know if the replacement floor sections have been redesigned with the dowels, or are they the exact same?

Looking at the photos of the new section that Mark posted up, I am unsure of the differences?

http://img.photobucket.com/albums/07...ps0a299803.jpg

Bang On, 100% Nail on the head - an inherent design fault with the E46 chassis!
This should have been rectified before continuing production as it was known to exist before 2003.
Yet production remained unchanged, except for the CSL where if anything the likelihood of the defect occurring was enhanced. :(
The term 'Professional Negligence' springs to mind! :whistle:

So now that mine is cracked and sitting in my garage while I decide the best route for repair what's the thoughts?
I'm totally in agreement that the new floor fix and resin injection will come back in years to bite in one way or another.

Would there Be a way to tie these mounts into some sort of rear strut brace to spread the load a little?

Concern would be loosing all the boot space in place of steel tubes as for me part of the CSL's appeal is that it has a usuable boot (in the dry obviously) :whistle:
From the rear struts forward would be ok though.

Then there is the repair plates. Again its into welding and heat, condensation, internal corrosion etc etc and at the end of the day will this actually stop it happening again or will it just rip out a bigger chunk of metal?

I think the load / movement needs to be absorbed and spread through the car rather than just the boot floor. Just a case of how?

I'm in a position now to try and only want to be doing this once.
Discussions and opinions please?

I saw some pictures of the result of the strengthening, where it just did as you said and ripped even more of the floor apart, but I can't remember where I saw them. It was shocking how bad it was though :smt120 !

Given that we are where we are, i.e., love theses cars but the feckers keep cracking, and that BMW offer a "fix" that we either; can get but are sceptical of, don't want, or, as in the Swiss guys situation, can't get, what does someone like Alx do?

Is a reinforcement plate such as the Reddish kit a bearable (no pun intended) comprimise? I'd have thought yes, but only with a structural foam intection to distrubute the load more softly through the plates into the body. Structural foam in itself is a good idea, the sandwich structure formed offers excelent properties, but only an option if it lasts and does not promote corrosion. When used in OEM design from the onset, the car body gets properly dipped in for corrosion protection, something we don't have the benifit of.

Is the foam itself going lead to that more corrosion? Maybe a little, but i'd have thought the main issue is the new welds them self / areas of the body where the original factory protection coat has been disturbed. i.e, foam or no foam, condensation will eventually get in an rust will start. If so, is enough being done in either the BMW cut-out-your floor method, or Reddish reinforcement plate method to corrosion protect welds / exposed metal on both sides of the weld?

Those who have had the BMW goodwill fix do have a life time guarentee, but I think we'd rather not ever have to use it.

Hi,

I finally had aome information from my local BMW garage.

Thet say that they can do the foam injection as a prevention, but they can't garantee that the cracks will not appear.

The thing is I don't really trust them...

In that case alex, i'd also not trust their insp where they sait it wasn't cracked. If your going to get it foam filled, get a second opinion first. Foam filling a cracked floor then trying to fix / patch cracks afterwards would be a disaster. Best, check yourself. I was told mine was fine, then Gareth found a crack in 10 sec. Need to knowcwhere to look.