Quick Links: Overview RACP RACP Specifics
Much more will come,
however, in my view, the work to fix the RACP issue is normally not a DIY work. If not done properly You have a great risk of just making things worse – and that irreversibly. I have seen apparently “nice looking” but in reality horrible work on this issue. Amazing what sealant and paint can hide! Cleaning, preparing and welding are serious matters in this department.
It seems as the top professionals in these matters are British. In my opinion you should only leave this job to someone who is experienced and you fully trust to do a proper professional job
My own M3 is due for a RACP Repair & Reinforcement. I have so far not been able to find any workshop in Denmark that I will thrust the job, so it will most probably be done in UK. In due course I’ll let you know my findings and experience in this process.
(Illustration above (not my own car) shows left rear anchor point for the sub frame. Left rear is normally where the problem starts and it can be inspected rather easily. If you have no cracks there, chances are good that there is none elsewhere. )
Overview RACP
The 1st photo to the right is marked with the 4 anchor points
for the rear axle subframe:
RL: Rear Left; RR: Rear Right; FL: Front Left; FR: Front Left
These 4 anchor points are where the sub frame bushings are
bolted to the body – and are thus the points that take up much
of the forces.
The 4 blue dots indicate where the threated holes are.
The blue lines following the inner edges of the wheel wells show
where broken welds are likely to be found. This goes too for the
trailing arm mounting pockets (also marked with blue).
The 2nd photo indicates with red the area you should clean and
inspect for cracks and busted spot welds – if you want a proper
job done. Cleaning is mandatory since just a thin layer of dirt can
hide problems.
The 3rd picture shows the original RACP panel, part 41 11 7 000 246. This part is NLA (no longer available), but may become available in future.
Very late in the production of E46 M3 BMW introduced an
upgraded RACP. To my knowledge this included some foam filling
in cavities, but is no guarantee for being crack-free.
One may ask why BMW did not detect the RACP issue earlier and
corrected it properly. I’m rather sure that BMW officially wouldn’t
comment on this, but I have a guess: The RACP issue is primarily
a fatigue problem so it only shows after some time. I can imagine
too that BMW did not foresee the extent to which E46 M3 “landed”
on tracks and in extremely rough driving.
So one must imagine that only a few claims were made in the
first years. At least some of these were repaired on warranty –
but it did not look like a mere general problem. Later, when it
became clear that it really was a general issue (for cars used for
more than “Sunday sightseeing”) the model end was too close to
really do something more costly. The upgraded RACP was only a
half-hearted solution. To really solve the problem the panel should
probably have been made of thicker steel – and perhaps even a
more fatigue stress resistant alloy.
RACP Specifics
Here are some typical examples of cracks and busted spot welds.
The pictures are from different cars, but make a good representation of the more typical cracks etc.
