"In this Special Series, I document my complete paint & body restoration along with the exterior upgrades to CSL specifications. 

In this entry, lines are crossed, we hit rock bottom, and we reset. We hike down the infamous subframe chassis reinforcements, and make our way back to the surface with a much bigger bill than expected - but it's all for the better."
-Matt

The original plan. 

In the context of the restoration, I focus this entry on the positive consequences of going in-depth on the topside reinforcement - albeit for my wallet. 

The complete, detailed documentation will be in the Special Series dedicated to the subframe chassis reinforcements. It's intricate, technical work that will require a lot more documentation than below. We want to go a step further in documentation by providing the engineering understanding of the chassis and the kit's design. 

The original plan was originally to reinforcement the topside subframe and lightly spray the trunk area in San Marino Blue to eliminate traces of Phoenix Yellow. The original plan ended up changing drastically. 

BMW left most of the shell on a grey sealer finish, with outlines having some Phoenix Yellow.

The original plan was to redo the outline in black to remove PY and leave the shell as it is.

Fixing rust. 

The previous owner had another brilliant idea of fitting aftermarket smoked LED tailights from China. The rubber strips on the rear lights were damaged and water seeped through the trunk channels, falling into the battery tray. 

It rusted the battery bracket straight to the dumpster, and left the battery compartment rusted. Luckily, it was still only surface rust. 

A respray was mandatory here, I expected it. 

Fully spraying the trunk. 

The trunk area was the only area where BMW properly put paint down on the interior shell. You can spot the obvious differences between the trunk's edge and the shell's dusted, misted paint.

The color saturation is the tell. 

Top side inspection. 

We first begun the work by sanding down the paint and sealer to bare metal, exposing any imperfections in the metal work, spot welds and unique topside rear rear axle carrier panel reinforcements. 

You can't really see much from here, you need to know what to look for when it comes to RACP reinforcement, top and bottom. 

As welding was part of the plan, most of the interior carpet was removed, along with its insulation foam. The rear seats had already been taken out, and the front seats were at the upholstery shop. 

Something wasn't factory. Can you see it? I'll give a hint: by the yellow tape. 

What is even that? I searched online, in archives, and ask a few long term E46 M3 owners, and none of us could figure out what this was. It appears to be a form of plate that was welded over where they assumed the rear subframe mounts pushed upwards. 

It may also be an access "port" they used to patch up a previous inspection. I will never know. 

The front subframe mounts sit below this angled front section of the RACP.  There was no way to tell its condition without cutting through the panel. 

The surgery begins. 

We officially got to work with the rear axle carrier panel reinforcement with the first cuts into its bare metal. I will provide a quick overview of the work. As a reminder, the in-depth process will be documented in the Special Series on the subframe reinforcements. 

The provided instructions are well detailed, and made our lives much easier fitting this. 

The front mounts. 

We first cut into the front mounts first to install the front bar and the triangular side pieces. Not showcased here is the metal pieces that reinforcement the front subframe mounts directly prior to welding in the front bar. 

The front subframe mounts are the first to weaken and crack. This is where it starts, and where most help, and repairs are usually needed. 

By reinforcement the mounts themselves, and connecting them to the chassis rails, we both relieve loads, and reinforce. 

The rear mounts. 

The rear bar's design requires to cut out the hump section. Cutting through this section reinforced our assumption about the welded plates being used to patch up a previous inspection over any sort of credible reinforcement. 

You can see the folded sheet metal coming together to create the RACP - and how the OEM design is not connected to the frame rails. 

The rear bar is 4 pieces kit, with frame rail plates on each side creating an extra layer to the rails and a flat surface to connect the 2 piece bar. 

The picture below shows the finalized assembly. It raises the floor slightly, and connect the two frame rails together. The lower section of the bar was welded in, and then sealed with epoxy to avoid rust concerns. 

All the spot welds were grinded clean. This shows the process half way through. 

Tapin' and sealin' 

With the front and rear bars welded in, their welds grinded and underpinnings sealed, it was tape to fully seal in the bare metal from the elements. With the car's exterior shell having been fully painted, an extensive masking and taping effort was required. 

It would have been much simpler to perform this work at the start of the process, but this isn't how build planning works most times.

If you're going to take on a complete restoration, feel free to learn from our "errors". 

The epoxy sealer got sprayed in overnight and was immediately sanded down. There's a limited time window to sand such coatings and we had to work fast. 

My madness begins here. 

It is at this point that it became painfully obviously how only respraying the trunk in San Marino Blue wouldn't be enough. Phoenix Yellow was everywhere and contrasts everything, ever more so against Blue. 

If you're going to do a complete color change, start with a Silver or Black car. You're going to save yourself thousands, if not 10,000$+. 

This is the unfortunately reality of a color change: it costs way, way more than a paint refresh to do it right.  

All of a sudden, I was seeing Yellow everywhere. 

Reminding myself that this was all covered in carpeting wasn't enough. I had seen too much. 

We found rationalization. 

For those that have been through topside reinforcement, and have done it right - or wrong, know exactly what I missed in the previous pictures. We forgot to stitch weld the upper of the new frame rail plates. This is a high load bearing component of the kit and it needed to be redone. 

The grinder was pulled out, and this section's sealer was sanded down. 

A few MIG welds later [...]

Bam! A one component sealer was rapidly applied to avoid rust concerns prior to a proper 2 component reseal. 

Urethane sealer was then applied across all edges, and a few holes were drilled for access to rust proof. 

Bam! Top side, weld-in RACP reinforcement was now complete. This is where most DIY'ers will end. Some will have their color codes matched in a single component aerosol urethane paint to dust the shell. 

Once more, in the context of a full color change, more was needed to do it right.  

Game time decision.

Our intentions with the work was to showcase a higher than standard topside reinforcement job, and something you should expect if paying out of pocket for professionals to do it. The chassis got rolled over in the booth, and booth time is money - a clutch decision was made. 

AH! I had found my excuse to rationalize respraying the interior shell - but to what extent? 

 

Perfection is the enemy of good. 

My car will have a full interior - spraying the interior shell is aesthetically useless. It will never be seen but anymore but those at the paint shop - and everyone one of you who are reading this. 

AH! I need to lead by example in some ways. I opted to respray the entire rear seat, and front seat area, leaving the dash in the car, along with a few accessories, and harnesses.  

I had finally found my limits.

The tape and masking job was extensive. Overall, the further disassembly, masking and paint work added around 15 hours to the timesheet. 

Alright, let's inspect! I pulled out the "SunGun". This is a common lighting device used by painters to mimic the sun's effect on paint. It brings out imperfections, and the metallic & pearlescent effects. 

Every picture that follows has exposure to this light. 

BAM!

Alright, alright, alright - let's go around the back. 

Nice! This was most initial focus, and remained the area I was most excited about. The E46 remains a practical car and the trunk gets used. Seeing it fully painted made me happy. 

The CD changer stayed in. Jonathan still thinks I should dump in, but the 90s kid in me says no. 

Back to the rear seat area, you'll find proper masking had been applied over the rear window area and the insulation foam underneath the rear shelf. This foam was dusted by BMW during the initial paint application. We chose not to. 

Some of the sound deadening was removed to weld in the front bar. Still, most remained by the front seats and got painted over. 

We opted for a light liner-type finish to spray the interior, with a coarser liner for the rear trunk area. The density will affect durability and resistance to scratches. 

The finish is un-cleared. Clear coat is expensive, and needless for a street car interior. 

It isn't perfect. 

A lot of parts were taped off. This means some yellow will still be present beneath some sections of the interior. Race cars get to permanently remove a lot of those, for a street car, everything that gets removed has to go back. 

For every hour you spend dis-assembling the interior, it's another hour you add to re-assemble it. This is where I put a stop to the excess on this build. 

Still, the most critical areas were properly sprayed. The outlines that were painted PY were now San Marino Blue. 

The upper door frame was fully sprayed as well. 

The front seat area was also sprayed, but it stopped by the front carpet section that remained in the car, below the dash. 

And most important to my OCD, the damn rust was gone. 

The underbody and interior restoration have become the two unplanned, major overspends in this restoration program. 

Still, I'm grateful to have had this done, but it isn't over yet. We'll need to inspect the underside again due to the welding. 

Up next: time for the fun part - it's becoming a car again. The last accessories get sprayed and reassembly begins.