E46 M3 RACP Repair & Reinforcement process - INTERNAL


Over the recent years more and more information and findings on this complex Rear Axle Carrier Panel have been discovered.
Nowadays we know more than ever about the INTERNAL sections of this panel from our determination to gain as much knowledge as possible about fault patterns and failure analysis from cars which get brought to us, or cars we've purchased for research & development.

Redish Motorsport are the first UK company offering RACP repairs to publicly discuss these new INTERNAL issues, offer our knowledge, show pictures and video examples (YouTube RedishMotorsport), and put into place an option to have these potential faults repaired.

There are 5 common areas of the RACP which are only accessible from inside the car which can suffer with broken spot welds and/or cracks:

  • RACP Front Cavity MIG Welds cracked.
  • RACP Rear Cavity Spot Welds & Panel cracked.
  • RACP Side separation from Chassis Legs.
  • Seat Panel Side Spot Welds & Panel cracked.
  • Seat Panel cracks around seat belt and/or child isofix mounting points.


Cost:

If your E46 M3 requires all 5 internal repairs inside the car then the additional costs would be:
The Redish Motorsport complete 5-stage INTERNAL Repair & Reinforcement Process costs:
£1316. including VAT

The breakdown is:
£20.50 Parts - (Sound Deadening Pad).
£971.50 Labour.
£104.67 Consumables (paints, sealers, cavity wax, amongst other things).
£219.48 VAT

(However, some cars may only need 1 of the 5 INTERNAL processes which would cost an additional £532. including VAT for example which is more palatable than needed all 5 INTERNAL processes at £1316).


Notes:

As strange as it may sound, the INTERNAL (inside the car) work takes as long as the UNDERSIDE traditional work. This is because when you are cutting metal, grinding, drilling, welding, creating paint/sealer dust debris, applying paints, sprayable seam sealers and cavity wax underneath the car all the 'fall out' debris just falls onto the workshop floor (after flying around).
Whereas when you try to carry out those same processes INSIDE A CAR with glass, leather, carpet, plastic, and all sorts of delicate, expensive, flammable, and sometimes irreplaceable trims, the 'fall out' or 'waste output' from those tasks flies around at high speed (propelled by the tool it's come from) and will land on these interior trims and would likely cause damage.
This is why we have to spend an awful long time removing so much of the car's interior, storing it, and the protecting what has to be left in the car (i.e glass, headlining, dash board, main carpet etc).
All this additional time unfortunately adds to the labour costs which make this INTERNAL process almost as expensive as the traditional underside process.


Process:

Most of these additional damaged panels are only accessible inside the car and therefore require a lot of the boot carpets, trims, carpet panels, door cards, as well as the Rear Leather Seats (bench and backrest), Fuel Tank & Diff Carrier Sound Insulation matting, Rear Side Bolsters, Rear Seat Belts & Isofix Brackets, and Plastics to be removed, stored, and protected before we can consider internal repairs.

We carefully remove all the interior from the rear half of the car (almost everything)!
We protect these removed items and wrap them in protective disposable BMW bodyshop covers, label them, and store them in our purpose built storage system.

We use a genuine BMW bodyshop disposable car cover to protect the car, exterior paintwork and glass. We use custom shaped hard card to protect the inside of the rear windscreen and inside of the rear side window glasses. We apply protection tape on high traffic areas like sills, kick trims, and B-pillars where we will be entering/exiting the vehicle and where static power leads and equipment will be brought in/out of the cars aperture.

Then we remove the complete sound deadening pad material over the RACP (later replace).
Also we remove the thick strong seam sealer beading over the RACP, Boot Floor, and Rear Seat Panel so we can inspect the sheet metal work of these panels closely for damages.

We cut open 2 rectangular access holes in the Rear Seat Panel to expose the broken RACP Front Threaded Receiver Upper MIG welds.
We stop drill the ends of the cracks, and carefully remove the entire factory (usually inferior) upper mig welds, clean the area and bare metal our workpiece(s), apply a weld-thru primer for additional protection. Then weld new penetrating mig welds into both Front Threaded Receivers and puddle the weld into the upper RACP cavity panel as well as welding the cracks.
Install Redish 005 plates and tack weld into place as covering panels for the Rear Seat Panel.
We also have a brand new 'unique-to-Redish' additional method of connecting the Redish V2 plates to the internal cavity panels whilst having this unparalleled internal access.

Drill out 10 spot welds, remove 4 MIG welds, and make a carefully planned continously thin and curved cut in the front edge of the Boot Floor Panel to allow access to the Rear Threaded Receivers and Rear Internal Box-Section of the RACP. After locating spot weld failures and drilling through them, and stop-drilling any cracks found, these damages get welded to repair and reinforce the effected problem areas found.
We use our brand new 'unique-to-Redish' additional connection method for further securing the Redish V2 plates to the internal cavity panels, before painting the inside of the hidden cavity.
Finally we close the cavity using the cars original Boot Floor sectional cut we made earlier.
This is welded to a highly OEM finish with 10 front plug welds, 4 side stitch welds, and a continuous 800mm weld line in the curved crease of the Boot Floor panel.
The continuous weld line is then ground/flattened down to almost disappear.

Next we stitch weld both sides of the RACP to the Chassis Legs, front corners of the Boot Floor, and rear corners of the Central Ribs for added panel security so it's not just relying on spot welds alone to hold itself (RACP) to the rest of the chassis.

Then we move onto the Rear Seat Panel and drill out the 6 broken spot welds (3 each side) holding the Rear Seat Panel to the Middle Chassis Legs.
These are replaced for plug welds, and also these panel lap joints are stitch welded together for added security.

Finally we stop-drill any cracks found around the seat belt or child's isofix mounting threads, v-groove the crack, and weld it closed using a manual pulse weld technique.
These welds have to be delicately smoothed/ground down flat so the seat belt anchors and isofix brackets can be later bolted back into place flush during the rebuild stage.

Now we have to vacuum you entire car and remove any loose seam sealer particles from the underside of the parcel shelf or anything which is going to later fall into our freshly painted areas. We continue to paint-prep by carrying out extensive degreasing using a panel wipe agent to decontaminate the bare metal worked areas.

We usually warm the panels up with infra-red lamps prior to painting (depending on the time of year due to ambient temperature).
We apply a first coat of Etch Primer to the bare metal worked areas inside the car.
Once dried, we then apply a coat of High Build Primer.
Then we can move on to the sprayable seam sealer process.
We protect the front of the car even more now with large cardboard sheets to limit the travel of a heavier matter like sprayable seam sealer.
This is applied to the RACP, Boot Floor, Seat Panel, and Chassis Legs inside the car.
Once this is dry we apply a colour top coat to the seam sealer which is usually your cars body-colour (for example Titan Silver, Carbon Black, Imola Red, Phoenix Yellow, Estoril Blue etc).

Then we move on to the real attention-to-detail finishes by cutting a new genuine BMW Sound Deadening Pad (black) to the shape of your E46's internal panel arrangement.
We use gentle, slow paced heat application and hand pressure to allow the glue to steadily warm up and not only fall into the contours of the RACP pressings but also bond itself tightly to make a further seal as well as offer sound deadening properties to combat Diff noise.

The final 'messy' job for inside the car is to carry out extensive cavity waxing through the RACP Front & Rear cavities under the Boot Floor Panel, Rear Seat Panel, Side Chassis & Mid Legs, Central Ribs, Spring Perches, and anywhere else that our specially designed long reach 500mm delivery wand and 360'degree application nozzle can reach.
We inject high pressure automotive cavity wax into these cavities which has excellent creep properties and initially rushes through the flutes and stamped pressings of the panels, but slows down as it begins to solidify as an automotive cavity wax should.
We're regularly able to inject the cavity at the middle Chassis Legs, and within 10 minutes confirm an effective 'creep' by witnessing the fresh cavity wax slowly dripping out of the side sills by the jacking points!

As you can imagine, we've tried various brands of consumable items like paints, sealers, and cavity waxes to name a few, and we are always interested in progressing and improving our repair methods, but we can assure you that what we currently offer is the best all round finish available anywhere today.

Now it's time to install and rebuild the car's interior which includes rear wiring looms, battery loom, all module trays, BM54's, Nav Drives, Video Modules, Bluetooth Modules, CD Changers, oddments boxes, Battery, Safety Terminal, Alarm Tilt Sensor, Petrol Flap emergency pull cord, Rear Light Bulb Carriers, and then all the leather, carpet, door card, boot floorboard & carpets, and rear bench and backrest seats.
(Just this rebuilding of the rear half of the car's interior can easily take 2-3 hours depending if it's a coupe or convertible).


VIDEO EXAMPLE TO BE UPLOADED HERE SHORTLY.