Reviving an E39 Door: Rust Repair, Clear Coat Fix and Exploring the Think on Paper Technique

Navigation
1. Introduction
2. The Think on Paper Technique
3. Part 1: Lower Edge Rust Repair
4. Part 2: Clear Coat Restoration
5. Links to products used

Introduction

Behold, my 2001 BMW 540i 6-speed manual. I've restored it to an outstanding condition. It's ready to race its younger self.

It's a three-pedal, shift-it-yourself, rear-wheel-drive, eight-cylinder rarity. It's more than just for show. I have put over a 100 000 kms during my ownership.

It boasts an understated design yet is very engaging to drive, even when compared to my 718 GTS 6-speed manual, which is purpose-built for driver engagement. The unique sound and feel of older enthusiast cars are fading away. That's why I want to preserve some these experiences.

About this door. Recently, I backed it up into a pillar:

Ouch. After a quick pause for colorful language, I came up with a plan to fix the damage. I got a door from a parts car ($250 CAD). It wasn't in the greatest condition. To bring the replacement door up to a quality standard, I did two things:

1. Rust repair
2. Clear coat repair (paint correction)

Below are pictures of the "new" door and some before and after pics of the rust repair:

And here are some pics of the the Paint Correction process. It's a type of scratch removal and clear coat restoration process. By removing the clear coat's top layer a little bit, we reveal a restored finish:

There we go, no more rust and nice and glossy finish. Much better.

Parts for these older cars are getting harder to find. Chances of finding a perfect door for a 20+ year old car are slim. I turned to an enthusiast e39 group on Facebook to maximize my chances.

The door I worked with was the best one I found after looking at 3 doors. It was actually in pretty good shape. The scratches were from transportation. The rusty edge had to be addressed though.

If the rusty lower edge wasn't fixed, it would soon be beyond the point of repair without me having to find a metal fabricator and doing sheet metal patching. A route I did not want to go down.

Why not take it to a body shop? Unfortunately, most just paint over the rust and it will come back. There is a way to address it properly, which is to remove the rust to bare metal before painting. Rust will grow under the paint if its not removed properly. When the paint bonds to bare metal well without rust getting in the way, there is no exposure to air and it guards well against future corrosion. So, that's what I set out to do and reverse this big eye sore.

Since it was my first time with rust repair. I used a technique I call the Think on Paper technique. Pretty simple but it works. Specifically, I call it the To Do List + Activity Log Method.

It's a sort of "rolling wave planning" as it's known in project management but combined with also rolling wave execution method. Somewhat born out of laziness to properly plan for smaller tasks but it does work well. I talk about how to do that below.

Think on paper: The To Do List + Activity Log Method

This technique is similar to solving a long math problem on paper. A skill I refined during my time in school for aerospace engineering. The technique of thinking on paper still really helps produces outstanding results while minimizing frustration.

I really like this technique for problem solving. I use it frequently. For example, when I make my to do list for the day, I divide my paper into two sections. On one side is a log of the activities as I do them and on the side is the original intended to do list.

By keeping history and tracking steps that I did while problem solving, it helps me to speed up execution over the long run. This is because there is often a need to explore tangents or switch tasks. Task switching is known to be extremely time consuming. By keeping an Activity Log, you can check what you did without having to remember it and resume efforts quickly. Otherwise, sometimes it may take up to a day to resume where you left off. It's a hack to move quicker towards good results while problem solving.

A quick mention on the "weekly to do list". I think this is the more important list on a day to day basis. Daily to do list are great but often the needle moving tasks slip as urgent tasks come up. By maintaining a separate weekly to do list, it helps to avoid the keeping busy vs being effective trap. Two lists are needed at the minimum.

Regarding the activity log, I can come back and refer to it to jump back into tasks if I wandered off the original plan - which always happens as you run into unknowns. So, I used that here.

Last thing before we jump into pictures and the specifics.

How did I know what steps to do? I watched a bunch of YouTube videos until I got a feel for the process. I am convinced learning off of YouTube is the same as when Trinity from the old movie The Matrix learns to fly a helicopter by downloading the skill directly into her brain.

Sure, YouTube takes longer than movie magic but imagine the alternate of having to go to a library and learning it from a book instead. With our smartphones, anything can be learned from YouTube, the internet, ChatGPT etc.

The internet is a like an evolving central nervous system of humanity's specific knowledge. Binge watch instructional videos for a bit and you'll be good to go.

Then, I proceeded with the repair. I wrote down the steps I am doing on one side of the paper, pausing and watching more videos if I felt stuck and using my Activity Log as a prompt to build the To Do list on the other side of the paper; as I learned more of what I needed to do.

I have used the same Think on Paper technique to perform new software implementations, build my ideas, solve math problems in school and various problem solving scenarios. It's a key technique. When problem solving, you should Think on Paper.

I do it digitally in Notion or OneNote by taking mini screenshots of each step if solving a problem on a computer - like when doing new software implementations, creating new features, or building out hairy long BI dashboards. It works well. Can review the steps if you get stuck to prompt the brain for how to proceed.

Here is what the end result of the Think on Paper: Activity Log - To Do list method looked like for this mini project by the time I finished it:

Below is a collection of pictures explaining the specifics.

Part 1: Inner Lower Edge Rust Repair

• Prep the Workspace: Found a flat table to work on. Covered it with a blanket and a plastic drop sheet for protection.
• Illuminate the Area: Employed a desk-mounted LED lamp for optimal lighting.
• Protect Surrounding Areas: Masked off the inner part of the door to prevent unwanted paint or damage.
• Inspect for Damage: Examined the interior and exterior lower edge, identifying paint bubbling. Used a sharp small flat-head screwdriver and metal wire brush to aggressively scrape off the affected areas.

• Deep Rust Removal: Much of the rust was tackled with a metal wire brush and screwdriver. Removed the seam sealer at the lower edge, revealing rust beneath. Continued with the flathead screwdriver and metal wire brush. Utilized a small battery-powered Dremel with a wire brush attachment and 100 grit sandpaper to clear remaining rust. Employed a hosed vacuum cleaner to manage dust from the Dremel.

• Outward Edge Inspection: Flipped the door to inspect the outward-facing edge. Noticed minor rust bubbling beginning to spread. Masked off the lower edge with painter's tape just above the rust bubbles. Initially used a flat-head screwdriver and metal wire brush, followed by 320 grit sandpaper. Opted for finer grit for the outward side to minimize unnecessary paint damage. For the inner edge, employed a flapper sanding disc attached to a drill for a quicker rust removal process.
• Rust Treatment and Painting: After prepping both sides, applied rust converting jelly, then cleaned with rubbing alcohol. Covered the outer-facing edge with Tremclad flat black rust-inhibiting paint for temporary protection until a professional touch up could be done. For the interior-facing edge, primed and painted with Duplicolor primer and gloss black paint for immediate finish, choosing these products for local availability.

• Accessing Hard-to-Reach Areas: Wrapped 100 grit sandpaper around a plastic card to access the edges where sheet metal folds met, reaching the bare metal for thorough rust removal.

• Continued the scraping and sanding. Started looking pretty good. Almost ready for paint.

• Inspecting the Other Side: Flipped the door over for a closer inspection. While rust wasn't a major issue, there were scratches I aimed to remove. Noticed running clear coat, suggesting a previous repaint, which I planned to correct with wet sanding to address both the scratches and the uneven clear coat.

• Treating the Other Side: Achieved bare metal on the other side using the same method: began by removing bubbling paint with a small flat-head, followed by a metal wire brush, sandpaper, and cautious use of a flapper disc. Applied gelled rust remover, then rust reformer paint. Waited 10 minutes post-gel application and 24 hours after the reformer paint. Applied two coats of rust reformer, despite the can recommending only one, for added protection.

• Reviewing and Proceeding: Examined the results of the flat black rust reformer paint on one side, then flipped the door over to apply the same treatment to the other side.

• Painting the Inner Side: Before painting, the inner side was well prepped, showing minor pitting from rust but otherwise in good condition. Applied flat black rust reformer spray in two coats: a light first coat, then a heavier second. Waited 24 hours. Then, added three coats of primer, three coats of gloss black, and three coats of clear, with a 10-minute interval between each for proper drying. I employed the technique of soaking the clear coat canister in hot tap water, inspired by the reputable ChrisFix YouTube channel. Though it seemed risky, further research confirmed its benefits. Heating the clear coat reduces its viscosity, allowing for a smoother application and a better finish from the spray can.

• Final Inspection: Examined the final results after completion. Not bad at all. Confident that the rust won't return.

My remaining concern: And what about the space inside the door, between the outer and inner parts? Could rust start growing from the inside? Yes, it can. I researched a bit more. If I did all this fixing, would rust just come back from the inside? I found out that rust usually starts where the paint gets damaged, usually when rock or something hits or chips it.

So, getting rid of it completely from where it starts makes sense. Also, I found out that you should spray some rust-proof stuff every year. It's much easier than sanding inside the door and produces better results. They use stuff like Lanolin or Cosmoline. It's sprayed through little holes in the door and frame and it stops rust by keeping air away from the metal. When I learned they use this trick on old steel bridges to stop rust for 50+ years, I figured it was the best low effort way to go forward.

Up next, clear coat restoration.

Part 2: Clear Coat Restoration

The rust issue was addressed. I thought about stopping but since I had the tools, I figured a bit more work would make the door look perfect, so I continued.

This process of restoring the clear coat is known as Paint Correction. It involves removing surface imperfections to reveal a smooth, glossy finish. I think of it like sanding: where hand sanding might go as fine as 5000 grit, using a tool like the Rotary Polisher is like sanding with an incredibly fine grit, from 8000 to 10,000. It's a sequential process similar to sharpening knives on various grits of whetstone.

This part was easier for me since I've tackled similar projects before. Also, I had done paint correction on this car when I first got it. Even then, I learned it through YouTube videos. I would definitely recommend watching a few videos before tackling this yourself.

A good polish makes a big difference from a workability perspective. It shouldn't gum up or turn into dust and fly everywhere, which is often a sign that too much speed and pressure are being used or that you're using poor quality polish. The polish itself acts like liquid sandpaper.

I recommend taking a conservative approach, using no pressure and the slowest speed possible (I used 600 RPM). Buffing becomes significantly easier with this method, specially if using a Rotary Polisher like I did. These machines are notorious for being challenging to handle, often risking damage by burning through the paint. Most sources would recommend a Dual Action (DA) Polisher instead, which is much easier to control. However, I had a this lying around, which I bought for only $60 about five plus years ago, so that's what I used.

• The starting point. The scratches were from me mishandling this very heavy door. Note the run on the clear coat.

• I cleaned and wiped the door to start. Then claybarred it with soapy water.
• Put tape around the major scratches and sanded with 3000 grit sandpaper. I tried to alternate between horizontal only and vertical only sets of sanding stages, checking if the previous stages marks were gone, allowing me to sand evenly. I was looking for a uniform haze which can later be polished out and the scratches would be gone.

• Progress was going pretty well. I noticed another small scratch near by and applied the 3000 grit haze to it.

• For the clear coat run. I started with a more aggressive 2000 grit then 3000 grit. In hindsight, It would have been better to wrap the sandpaper around a solid block, instead of a foam block, for the clear coat run. With the foam block, I think I reduced it only by 80% before burning through the clear completely in one area and stopping.

• A bit of the clear coat run near the left that I couldn't get out is visible below. The sanding wore down the edge much faster than the front facing area. Definitely would recommend extra care when sanding around an edge.

• Good enough. I moved forward. Now, I had two areas with 3000 grit sanding marks, while the rest of the door remained untouched. At this point, I could have started with the buffer, but to speed up the process, I applied 4000 grit sandpaper to the entire two sections. By hazing the door with 4000 grit, it would turn out much better once buffed, with a lower chance of the sanded areas standing out — this is a blending technique. Sanding with 4000 grit also eliminates 'orange peel.' Orange peel refers to a finish where the paint doesn't smooth out completely flat but instead has a subtle texture resembling an orange's skin. Even new cars typically have some degree of orange peel. By removing it here with the 4000 grit, I achieved a true near mirror-like finish.

• I used three things here: an old Dewalt rotary polisher, Meguiar's Soft and Hard polishing pads and Scholl Compounds S20 Black All in One Car Paint Compound. I find this compound works really well. I noticed a shop using it. I've tried other compounds in the past, like Menzerna, and I've found this one to work best for me.
• The process here is to first buff with the hard pad (red) and then the soft pad. The hard pad eliminates the sanding marks but leaves a slight haze which is removed with a quick run from the soft pad. I used 600 RPM speed for everything. I'll include links to what I used below.

• I would do a pass with the buffer, wipe, check and repeat.

• The surface reflections started to look really sharp, even before the soft pad.

• I did a quick run with the soft pad, wiped it down, then applied Opti-Seal. This next-gen synthetic wax requires just one or two drops to quickly coat the bare surface. It lasts longer and is easier to apply. Additionally, you can apply it while the car is still wet, which is handy as it eliminates the need to dry the car before application in a typical scenario. I've been using this stuff for years.

• Some final pictures.

• There we go, all done, with a mirror-like shine to match the rest of the car.

If you've made it this far, amazing. I appreciate you taking the time to dive into my journey with the E39.

If you enjoyed this detailed exploration into automotive restoration, or if you're curious about what's next in my projects and thoughts, consider subscribing to the blog.

In upcoming articles, I'll be exploring ideas from books I've read, discussing productivity tools and techniques, and exploring the topic of motivation, digital entrepreneurship and the digital nomad lifestyle.

List of Products Used

1. Chemical Guys Microfiber Cloth
2. Micomlan Led Desk Lamp with Clamp
3. Pre-Taped Drop Cloth
4. Metal Wire Brush
5. Dremel Lite 7760 N
6. 120 Grit Sanding Flap Disc for Cordless Drill
7. 100, 320, 2000, 3000, 4000 Grit 3M Sandpaper
8. DeWalt Small Cordless Drill
9. Painters Tape
10. Dominion Sure Seal Gelled Rust Remover
11. Flat Black Tremclad Automotive Rust Reformer
12. Duplicolor Automotive Primer
13. Duplicolor Perfect Match Automotive Paint - Universal Black small (for the non-outside facing edge only)
14. Duplicolor Clear Coat small
15. Mother's Speed Clay 2.0
16. DeWalt Rotary Buffer (you'd probably be better off with a Dual Action instead of Rotary but this is most similar to what I used)
17. Scholl Compounds S20 Black All in One Car Paint Compound/Polish
18. Soft Meguiar's Soft Polishing Pad (check diameter vs your machine)
19. Hard Meguiar's Hard Polishing Pad (check diameter vs your machine)
20. Opti-Seal Synthetic Wax