My second SPI project- 1998 BMW M3

[95maxrider]

A few years ago I did a very amateur attempt at "rust repair" on the rear quarter panel of my 1998 BMW M3. Well, that work had started to fail and rust bubbles were popping through. Long before I purchased the car in 2015 it had been t-boned and poorly repaired, and these are the results of that. Here's what it looked like three years ago before I did my janky repairs:

And here's what it looked like before I started the project a month or so ago:

I knew that I was going to need fresh metal to do this properly, and thankfully since then I taught myself how to "weld" and "paint". I bought a replacement section for the outer part of the fender, but I needed something for the inner section too, so I found a car being parted out locally and went to chop out what I could.

There were some other rusty areas that I wanted to repair at the same time:

Under the DS tail light:

And around the trim on the trunk:

Thankfully I now also have a big media blasting tank, so I can get rid of rust correctly.

I started by taking it down to bare metal to see how far out the previous damage extended. I think I counted something like 9 layers of primer/paint on this panel! The original paint, the hack repair done before I bought the car from when it was t-boned, and then my first hack job.

Lots of filler down here too

Oooh boy

The inside of the wheel well was all crumpled up from the accident. Welding this was going to be a real challenge.

So I started by cutting off the outer panel, and was greeted by an unholy mess on the back side of the inner panel.

I then cut out as much of the inner panel as I could, and blasted the rest with coal slag to prepare it for welding and eventual paint.

This is where I want to note that according to my measurements, this inner sheet was something like 24-25 gauge sheet metal, and the metal remaining on the car was even thinner due it parts of it having started to rust. As someone who barely knows how to weld, this presented another challenge.

I eventually got it welded up as best I could. Some of the areas that were tucked up in the body were so hard to access and the metal so thin that I just couldn't get them to weld. Not to mention I was trying to get the shape of my crumpled inner panel to match up with the one I cut from the other car. I eventually had to put my OCD aside and just accept it wasn't going to be perfect.

 

[95maxrider]

I decided to cut out some more gnarly looking metal and replace it with fresher stuff...

And then spent a LONG time test fitting the outer panel. I started the test fit going from left to right, but it wasn't until I got everything on the left dialed in that I realized I should have gone from right to left! The gap with the door was all messed up, so I had to re-do a whole lot of work in order to get the door gap corrected.

But eventually, I got it done. I didn't put any gap (usually 1/16" IIRC) between the panels, as I didn't want to risk blowing through to gap. I am a complete amateur after all. This also led me to keep the settings a little low on the welder. It would have been one thing if I had access to the back of the panel and could use a copper heat sink, but I didn't, and so I welded it up with basically no gap and slightly cold weld settings. Sure enough, I didn't blow through it once, but the lack of gap did cause some warpage when the pieces couldn't expand properly when they heated up. I did blow each weld off with my air gun to keep the temps down though. I did a few rosette welds along the door curvature where the two pieces met, but for the most part there was a big gap between them that I later filled with glass filler.

Then I pulled the car out to strip off the rest of the paint. I got some paint stripping discs for my angle grinder and got busy! I discovered some previously unknown body work and a lot of filler up around the window...

So here's the rust under the DS tail light after peeling away some paint:

Stripped

And blasted with coal slag. Bye bye rust, and hello hole!

And the same for the trunk rust:

All clean!

 

[RenewAP]

Nice job. Be sure to get some cavity wax inside after all painting is complete, it will double the life of the repair.

 

[RosharonRooster]

Dang rust in a 98. That's when I graduated high school. Feeling old in this topic

 

[95maxrider]

Nice job. Be sure to get some cavity wax inside after all painting is complete, it will double the life of the repair.

Oh yeah, that's part of the plan!

Dang rust in a 98. That's when I graduated high school. Feeling old in this topic

Hey, I'm only a few years behind you! The rest of the car is in pretty good shape rust-wise, it's just the consequences of that old accident and poor repair job.

 

[MJM]

Much respect fixing the rust issues. You've done a good job by not cutting corners. You have also learned a new skill in the process.

Excellent thread outlining what you have done including pictures. I'll be watching this thread for future updates.

Job well done, thanks for sharing!!!

 

[95maxrider]

Much respect fixing the rust issues. You've done a good job by not cutting corners. You have also learned a new skill in the process.

Excellent thread outlining what you have done including pictures. I'll be watching this thread for future updates.

Job well done, thanks for sharing!!!

Thanks, I've got plenty more to post, just need some time to put it all together.

I'm self taught with no professional experience, learning from books, YouTube, and this forum. I'm always looking for ways to improve, so if you see something you think I did wrong, or could be done better, please let me know!

 

[95maxrider]

With the car back in the garage it was time to break out the welder again and get rid of the holes in the trunk lid from the old spoiler. It wasn't a factory spoiler, and I think the E36 looks damn good without one, so I wanted to get rid of it. When I removed it I also saw it wasn't sealed up with anything, so it was probably letting some water into the trunk.

Access inside the trunk was decent on one side, but inaccessible on the other, so the welds weren't great. But I eventually got them good enough.

And I found out why there was so much filler under the rear window:

I wonder if those are remnants from previous stud welding/pulling? The metal around the holes seems awfully smooth for that.

I did a few rounds of proper cleaning of the metal with the SPI waterbourne wax and grease remover, and laid down a few coats of epoxy primer. This helped highlight some damaged areas that I couldn't see before, like this one by the tail light:

In my excitement/nervousness to spray the epoxy, I forgot to tack rag the surface before spraying, so I had a lot of debris in it and I had to waste a lot of time smoothing it out before moving on. I eventually laid down some of the 3M Platinum body filler and got things level.

Since I had gone through to bare metal in a number of places, I laid down another coat or two of epoxy before moving onto the 2K. Once again, I had globby areas like the ones shown below in some spots, and as a newbie, I'm not sure what to make of them. Did I just get my overlap wrong in that pass? Was I moving too slow with the gun? Most areas turned out okay. I'm using an LPH400 at 26 psi for epoxy and clear, and 20 psi for base.

Can anyone hazard a guess as to what I'm doing to cause that?

During the paint phase I was under a huge time crunch to get the whole job finished before the final race of the year, so I didn't sand certain steps nearly as well as I should have, and it came back to bite me. I eventually was able to get things smooth enough for the base coat, but it could have been even better if I had more time. I sprayed thinned epoxy as sealer over the 2K, and while it sprayed better/smoother than regular epoxy, I got a few areas of the globby stuff like shown above, so I had to smooth out all of the sealer before spraying base. I took it up to 600 grit, but I think 800 or 1000 would have been even better if I had the time. Thankfully I sprayed two coats of sealer (instead of the recommended one) so I didn't sand through in any areas to metal or 2K.

Thankfully the base went on great, with only one small run where I got my overlap wrong. I did two coverage coats, and then I tried my hand at a drop coat to cover/hide any mottling/striping. I had plenty of that when I did my hack job three years ago with rattle cans, but this came out perfect!

I used the SPI Production Clear and sprayed 4 coats, but it didn't go down as smooth as I was hoping, especially on the horizontal surface of the trunk. There's a lot of orange peel in the finish, and I need to spend a lot of time cutting and buffing it. I thought I was spraying it on wet enough, but I guess I wasn't. How can I fix that in real-time as I'm spraying? If I see my first coat isn't smooth/wet enough, can I immediately lay down another layer on top? Do I need to treat horizontal surfaces different than vertical ones?

In the end, I think I can save it with cutting and buffing, but I'm embarrassed by the initial finish. But I got it done the afternoon before the race, so I'll take the win where I can get it.

Even with the poor finish, it sure has great shine and depth to it! I'm not sure how people can blend this stuff with older clear coat, even if it's in good condition and shiny, because it just looks so good. Granted, that wasn't the goal on this car, since the paint/CC is shot on the two PS doors, but I'm just curious. This job is to tide me over for a few years until I can respray the whole car in the factory Estoril Blue, like this:

Drool....

 

[aviator8]

Can anyone hazard a guess as to what I'm doing to cause that?

That is cratering caused by heavy application.

 

[1A Rock]

The globby spots just look like too much epoxy, any time I spray too heavy or too slow I get something looking like that. Nice job.

 

[95maxrider]

I figured I would wrap this thread up with pics of the cutting and buffing results. I used something close to the JimC method:

Assilex 1500 dry
Buflex 2500 dry
Trizact 8000 dry
ACA 3D 510 on a foam pad
ACA 3D 520 on a foam pad

For whatever reason, the orange peel/finish on the top of the trunk was horrible, while the finish on the vertical panels was acceptable. I'm not sure if it had something to do with the top of the trunk getting sprayed last in the process, or the flow from the fans behind me, but it was bad. But since I sprayed four coats of clear I figured I could sand it down pretty close to flat. Although I had done a little cutting and buffing on my first project, this was the first time I was able to take my time and really do it until I was happy. And in the end, I was very happy!

Trunk before:

Trunk after:

Rear quarter before:

and after:

C pillar before:

and after:

I've owned this car for 8 years now, and its primary purpose has been racing in rallycross, so the appearance has never been a top priority. It didn't help that so much of the paint was trashed, so I never thought it would be worth the effort to do more than hit it with the power washer. But with it looking so good in the back, and with the contrast so great with the other panels, I thought I would finally detail the whole car. The paint on the passenger side is some junky respray, while I think the paint on the driver's side is original. In the end, I was able to bring back a lot of shine, and the new paint doesn't stick out so bad.

So that wraps up this project. I made a lot of mistakes, and learned a lot from them, so my next painting project will be ever better

Any tips or feedback would be appreciated, I've got a lot to learn!

 

[123pugsy]

Looks good.

Thanks for sharing.

 

[hapcj7]

Nice job on the cutting and polishing! What basecoat did you use?..Did you find the production clear to be difficult to cut and polish?... PC is known to get "hard" vrs the Universal clear which stays on the softer side...

 

[95maxrider]

Nice job on the cutting and polishing! What basecoat did you use?..Did you find the production clear to be difficult to cut and polish?... PC is known to get "hard" vrs the Universal clear which stays on the softer side...

For base, I'm a little ashamed to admit I used PPG Shop-Line Plus, since this is only a "temporary" paint job.

Yeah so due to the timing of my race the day after laying down the clear, I wasn't able to start cutting and buffing for more than a week after I painted, so I was pretty far outside the ideal time window. Since I don't really have anything to compare it to, it's hard for me to really say anything about that, aside from it took many rounds of cutting and polishing. Wasn't a fun or quick process.

 

[Whitesnake]

Looks great! The old paint looks much better as well. What did you use for a polisher?

 

[95maxrider]

Looks great! The old paint looks much better as well. What did you use for a polisher?

Thanks! I have a Flex 3401 Dual Action and use a variety of foam Lake Country pads.

 

[Whitesnake]

Thanks! I have a Flex 3401 Dual Action and use a variety of foam Lake Country pads.

Nice! The beast! I have the slightly updated version…xce 10-8-125. Little smoother but they say the original is a touch more aggressive. Good polishers for sure.