Rebuilding My 1988 US-spec M5

[jhh925]

So I took a first swag at cleaning up the battery box. When I first took out the trunk liner parts and removed the battery, it was obvious that there was rust & corrosion in the box, likely from a leaky battery. My main concern was that whatever had leaked out of the battery and into the box had also dripped down under the box and created issues in an area that I don't know how to get to.

My plan was to "curtain" off the battery box and media blast the box in place. Things went mostly according to plan, though it became difficult to do more than a few seconds of blasting at a time before the media would start to fill up the box.





After some blasting, I think I'm OK with the existing box. I'll likely curtain just the box off again and give it another blast. That "after" pic isn't great, but if I get close up to that reddish residue looks more like film left over from the POR15 rust remover. The only damaged metal I'm seeing is that a portion of the forward battery hold-down is rusted away.

The better news is that I also managed to squeeze my bore scope into a few spots under the box (I'll edit this post with a pic if I can get the rig set up again), and I didn't see any rust at all under the box. It was dirty, but no corrosion that I could see. If anyone has any advice on how to get some primer or POR15 under there, please let me know, but my current thinking is that I'm not going to attempt to remove or replace the battery box.

EDIT: I got motivated and stuck the borescope in there again. After yesterday's cleaning, the scope actually slipped in more easily.





Those were the two dirtiest spots I could find. I'm pleasantly surprised a the lack of corrosion in there, and I think I'll leave the box in place. Just clean it up a bit more, POR15, paint.

[tig]

I didn't know about this thread. Regret. Fixed.

[vinceg101]

Given the condition under the box (good) I think your best bet is to get some good/decent rust-preventative primer (Rustoleum, Krylon) or even some Ruststop (Eastwood), see if you can use one of the plastic "straws/nozzles" (sorry, don't know the proper name) you get on brake cleaner etc. and get it in there under the box.

As to the interior of the box I would likely use a Dremmel tool with wire brush wheels to get into the tight corners (you will likely go through a lot of them, they're pretty fragile little things). Or you can put on the stone wheel bit also.

[jhh925]

Vince: Yup, getting the inside of the battery box was a total pain. I used a wire wheel on my drill to start, but as you note, that won't get into the corners. I'd considered using a Dremel, but I don't think HF carries enough of those wire wheel bit kits in their entire inventory to get that job done. So ... I ended up media-blasting the box a couple of times and scrubbed in that gap under the box by threading small rags through that gap. I knew the media blasting was going to be super-unpleasant, so I hung sheeting & taped off as much stuff as I could. I still ended up wearing glass grit everywhere. But the box got clean! Then I did a couple of coats of POR15 and then primer. Haven't painted it yet, but my hope is to refresh the entire trunk and I'll complete the battery box at that time.

Speaking of refreshing the trunk, if anyone knows of a good source for getting replacement felt padding (similar industrial look, similar thickness, wide enough to be able to cut the entire part without a seam), please let me know.

Also, great call on the Eastwood stuff. I think you may be taking about EASTWOOD INTERNAL FRAME COATING? It comes with a hose so that you can snake it into nooks & crannies. I was planning on using it in the "C" channel behind the rear valance and in the rockers, but using it under the battery box is a great call as well.

In any case, I'm continuing to make progress. The irony of the COVID situation is that with the stay-in-place orders I have plenty of extra time to work on the car, but getting parts has become more difficult. FCP & ECS orders that used to take a few days are now getting stretched to a couple of weeks. I assume that various shutdowns in the supply chain are affecting all of this.

The practical result for me has been that I have had a bunch of sub-projects (front & rear strut assemblies, diff refresh, some painting projects, front euro bumper mounts) that have been just a part or two from completion. Most of that has resolved, so I should be able to start putting the suspension and undercarriage back on in the very near future. And that's key because ... I think I found a shop that can do a good job painting the whole car. But getting the car there means it has to be a rolling shell (including steering and the parking brake). I would really like to get the car to them as soon as possible in the hopes that they can spend a bit more time & attention on my car while their business is slow.

Here's the install of the front euro bumper mounts. First, these are the donor mounts that took forever to get here (literally three round trips between here & AZ; thanks USPS).



US bumper shock tubes cut off and front tow hook assemblies removed:



Euros welded in:



And after seam sealer, primer & paint (actual 2k BMW 086 Schwartz!):



Diff refresh. Goal here was not to rebuild the entire thing, but instead to reseal it and make it nice & purty. And internal inspection showed that the bearings & races were pristine, so there was no reason to go beyond just a reseal anyhow. Oh, BTW, if I haven't said it before, I suck at remembering to get the "before" pics, so I've got nothing showing how grimy this was to start with.

Painting the case & output shaft caps:




Fully reassembled:



Starting to put the undercarriage subassemblies back together.









Since those pics were taken, I've also pressed the rear spindles back into the RTAs. At first, I put the RTAs back onto the rear subframe and then tried to press the outer spindles in. That was a total fail. Some research here on the forum indicated that pressing / pulling those outer spindles was a real pain, and it took me a while to remember how I'd done this last time. Of course, if you have the RTAs off the car, no special tricks are needed to get the spindle back in ... they can just be pressed into the bearings on the press. So, I took the RTAs off again, set up the handy-dandy HF 12-ton and they slipped right in. Forgot to get a pic, of course. I used a 46mm impact socket on the inside to support the inner race as I pressed the spindle in from the top.

I also got my SEM seam sealer sprayer set up to shoot the front & rear valences (both are new euro parts) and the repaired frame rails. Here's the front valance undergoing final inspection:



And the frame rails (sorry for the shitty pic):



One thing that's painfully - painfully - apparent to me here is that the SEM seam sealer isn't beige - not even close. It's so yellow it makes me want to go apply to the University of Michigan so I can hear all about how it's really "maize." I'm not sure what I'm going to do here. Options could include spraying some black / olive drab paint on there to "dirty" it up a bit and mimic the original factory overspray, or buy more SEM in both "beige" and black and mix them together to see if I can get closer to the look of the 30-year-old factory beige coating. The contrast to the old sealer is so stark that I really don't want to leave it like that.

Last update ... I know it can be a bit controversial around these parts, but given all the effort I'm putting into getting the undercarriage looking new, I didn't want to have dirty, hazy, worn-looking wheel wells as the backdrop for all that. I tried my best to clean them up as-is, but calcified BMW protective spray (not sure what it was ... creosote? Whatever that whitish-yellow crust is that's in a variety of palaces underbody and in the engine compartment) had gotten crusted up with embedded sand & grit, and the condition of the paint in there was pretty bad even at its best. So, I decided to respray the wells. After getting some detailed paint prep advice and spending several hours per well getting all the caked-on crap out of there, I resprayed with matching 2k BMW 086 Schwartz paint. I'm pretty pleased with the result even if my iPhone isn't capturing it very well.

After prep:



After painting:



That's all for now. I'm hoping to have the shell back down on the ground on its own wheels & tires and then off to pain in the next couple of weeks - assuming I can find all the needed parts in storage. Ugh - fingers crossed ...

[Nick1984]

Wow, great progress! and nice documented!
I will keep folowing this thread!

[jhh925]

Time for an update. The stay-in-place orders + working from home + general slowdown in business has given me puh-lenty of time to work on this beast. The thought also occurred to me that with the business slow-down, I might have an easier time of finding a bodyshop to do a full-body repaint. With that in mind, I've been focusing on getting the car back down on its own wheels so that it's legitimately a "rolling shell" that a body shop could work on.

So, after finishing the front euro bumper & valance work, I turned to assembling & reinstalling everything underneath. Rear subframe laid out in prep for reassembly:



And installed:



Fronts as well (brake caliper is there just for dry fitting):




And back down (almost) on the ground sort-of-kind-of actually looking like a car:



For now, I've found at least three shops that have at least some interest in the painting project. I wish I'd started on talking to them sooner ... no surprise, but it's taking a fair amount of time to get them to come out & look at the car, get an estimate, etc. Given all the time I've recently been able to put into the project, the March 2021 completion date was actually starting to look doable, but now it feels more like the painting part will take a lot longer than I'd hoped.

In other news, I got a few more parts back from powder coating & upholstery. (Sunroof slider is pictured below.)





I've also made some progress on converting the engine harness & management over to Motronic 1.3. Specifically, the hope is to preserve the existing S38 harness as much as possible. Grossly oversimplifying here, I'm looking to essentially put the M1.3 components at one end of the harness and the M1.3 ECU at the other end. That latter step will require converting the old harness from a 35-pin ECU connector to a 55-pin. As luck would have it, the actual wire terminal ends are pretty much identical between the 35-pin and 55-pin connectors, so I'd assumed that in theory I ought to be able to de-pin the 35 and re-pin the terminals into the 55. Easier said than done.

De-pinning the 35 was easy-peasy:



... but there 55-pin is designed a bit differently. In particular, each wire & terminal is threaded through a both a guide board and a "gate" board of some sort. Those holes on those two parts are lined up in such a way that even if you try to de-pin the catch on the terminal, you can't pull the wire out. Instead, you have to separate / delaminate the guide & gate from the actual terminal board, and then de-pin the connections. This was a total PIA and I spent an entire evening trying to figure this out, and basically ruined the 55-pin parts in the process:



Luckily, I've been planning for the wiring project for a while, so I've been collecting extra M1.3 harnesses & parts along the way. And then on this past Tuesday I totally lucked out. My local shop was tossing the engine harness from a first gen 750iL, and it turns out that those harness have three - THREE!! - 55-pin connectors. Now that I had some sense of what I was doing, and didn't care about the wires on these connectors, I just "shaved" the wires down, pulled off the guide & gate, and de-pinned all the terminals. Clean & easy.



And just to confirm, I test-pinned one of the terminals from my S38 harness. Fit right in. And it's not shown here, but the terminals will lace right through the guide & gate plates as long as you do it before reassembling the three connector parts. That is, I'll need to lace all of my wires from the harness through the right holes in the guide & gate plates before doing the re-pinning.

[tig]

Incredible work, Sir. Incredible.

[jhh925]

Made some significant progress today! First some background. As mentioned earlier, I've been planning on getting the car fully repainted, and towards that end I've been talking to a couple of body & paint places recently. The cost estimates so far have been about what I was expecting - or even a bit on the low end. Body shops are suffering as much as everyone else, and this is a decent job if the insurance companies aren't sending you a ton of work.

But then, in talking about my experience with a buddy who's in the biz, he mentioned that I ought to go talk to a local guy who's more in the full restoration biz. As luck would have it, the guy (Roger) has a shop just down the road from me and literally a stone's throw from my storage unit. It turns out this guy has been doing some pretty high-end restoration work by himself in a 4-bay shop he also built by himself. We hit it off pretty well, and he came to take a careful look at my car. His advice? "Don't paint it!" He ran the paint meter all around the car. Except for one spot that likely has some filler (and it's also looking like the hood has been repainted, but we're not sure on that yet), the paint is all original. So after batting it around for a couple hours, his suggested strategy is:

• Get a good "pointless" dent repair guy to fix all the little dings & such above the "schutz line"
• Get the car trailered to Roger's shop
• Do the required metal work below the schutz line (welded in holes from US bumper light wires, repairs to rockers, etc.)
• Re-schutz and re-paint.

That will keep the paint mostly original and likely cut way down on costs & time - or at least the money & time will be spent on keeping the car closer to the original. And this restorer guy is likely to do a much better job. I don't have pics, but he had a few projects he showed me in various states of completion (including a drop-dead stunning MBz 500E with a full-body repaint that was better than original).

So, after getting a referral, I lined up a good dent guy. Four hours in the garage and I'm amazed. There's more to do, but I'll try to give a sense of his work. Of course, in keeping with the fact that I can't properly photo-document any of this stuff for shit, I'm not sure if this will really give a proper sense of the improvement here.

Example of a door-ding before (actually, this was taken after the guy had done his first few probes, but it gives you a sense):



After:



In action:



And here's the worst ding. Getting to the back of this one will be a puzzle. I haven't pulled the foam padding off from the inside of the C-pillar, but it's feeling like there's at least one more layer of sheet metal right behind this.



In other news, I'm aking progress on the Motronic 1.3 conversion. I'm hoping to post some specifics here (and in particular, the pin-to-pin conversion when going from the 35-pin to the 55-pin ECU connector), so this update is just one small detail: In mapping the old pins to the new pins, I noticed that both M1.0 and M1.1 fire the injectors in two banks in the following sequence: 1-2-3 then 4-5-6. But M1.3 fires them 1-3-5 then 2-4-6. I'm not sure why they made that change (one of the gurus here thought it could be performance or more likely because the revised sequence helped with emissions), but I figured the best bet was to swap the #2 and #5 wires so that the new '179 ECU would fire in the sequence designed for M1.3. So, I opened up the injector wiring harness, did a little surgery, and threaded new jumper wires inside of the existing injector harness:





The cuts in the plastic looms were wrapped with Tessa tape before re-assembly, but naturally, I forgot to take a pic of the coolest part of the job. ¯\_(ツ)_/¯

[tig]

I view the not needing to paint as HUGE news. Congrats on that. I like Roger.

[jhh925]

I view the not needing to paint as HUGE news. Congrats on that. I like Roger.

Do you know Roger? Man, you seem to know everyone.

Anyhow, my dent guy is back today. I'm stunned by the results he's getting. Here's a visual on his progress on that C-pillar dent. Remember, there's no way to directly access the backside of this dent because there are multiple layers of metal in that part of the C-pillar. So, this improvement (so far) is almost all due to working from the front.

"Before" (one from before the car was disassembled and one from Tuesday):




And currently (the haze is from a waxy polish he's using to protect the paint):

[jhh925]

OK, so I know I'm obsessing too much on this one small section of the car, but I'm fascinated by what this guy has done with his bag of tricks to pull a dent that I thought for sure was going to have to get filled & repainted. Here's his final product:



I have to admit that this camera angle is sort of a cheat; the light in the garage is pretty bad and this was one of the few angles that clearly shows the fixed area with a nice clear reflection of the repair. With the naked eye, the area still shows remnants of the repair. Regardless, I feel like I've found a brand new tool!

[jhh925]

Quick update: The restoration shop nearby should be ready for the whole car next week (fingers crossed). The hood has already been delivered:



I was at the shop over the weekend, and Roger had already done a fair amount of work on the top side of the hood. We had been worked that the hood had been painted at some point, but Roger's paint meter said, "Nope, original paint." The improvement that Roger had made with just a coupe hours work was pretty amazing. Of course, we got to talking ... and I forgot to take pics. Next time.

In other news, I'm continuing to collect bits and parts for the motor, including getting a bunch more parts back from the zinc plating shop. The local shop I'm using in San Leandro has a brand new zinc plating line ... the result so far have been amazing. Here's a before and after on the alternator.





Here's the current status on the motor. With the accessories slowly going on, it seemed like the right time to start fitting the engine wiring harness back on.



Next step will be to splice in a new 4-wire O2 connector and fab a new mounting bracket that will hold the O2 sensor-to-harness connector plus hold the other wires that snake down from the lower left block to the underside of the car.

[jhh925]

Making slow progress. The "slow" part is a bit frustrating, I guess ... given that I'm working from home, I have plenty of time, but parts are harder to get, and I'm at a stage where I'm highly reliant on others (e.g., body & paint).

On the engine wiring, I'm mostly happy with the change-over to a 4-wire O2 sensor. I cut the 3-wire harness-side connector off, then put a 4-wire connector in. However, because the 4-wire setup has two signal wires, you can't just splice the 4-wire connector into the existing harness. Instead, I bought a length of new, 2-conductor (18 ga), shielded wire and I'm using that to carry the low voltage signal all the way from the connector to the ECU. That's the gray wire in the pic below. Since the existing engine harness is in really good shape, I obviously won't cut the original plastic loom off. It's not ideal, but the gray wire will just run parallel to the harness, run all the way through the firewall grommet and straight into the ECU. I'll be using the original wires in the existing harness for ground and the O2 sensor heater. Also, since the 4-wire connector is just a standard part on a bunch of these cars, I'm able to use the connector bracket from an M30-B35 (a bit difficult to see in this pic - it's cut off an old steel "loom" from a B35 what shields the heavy starter motor wire running from the alternator to the starter). That bracket also gives a handy spot to mount the 2-wire connector I spliced in for the ground and 12v+ lines.



I'd also sort of hoped to re-jigger the location of the purge valve. On an M30-B35 motor running Motronic 1.3, the purge valve is mounted on the underside of the intake with the purge line running over the motor to the charcoal canister that sits front-right next to the ABS pump. I was able to fab a bracket that could hold an M1.3-style purge valve underneath the ITBs. I think it looks nice & clean, and the purge line can run from there along the original path along the front of the motor:



But if I put the purge valve in that position, then I run into the same wiring issue I have with the O2 sensor. That is, in the original harness, the purge valve wires are totally in the wrong place and run along the front-right wheel well up to the purge valve / relay / barometric pressure switch assembly that sits above the ABS pump. I can't just pull those wires out of the original plastic loom (there's a splice hidden in there somewhere), and if I just orphan them over there, then I'll need to run new wires from the M1.3 valve parallel to the existing harness, through the firewall grommet and into the ECU. That feels like too many "extra" wires outside the loom. Probably easier to just put the new purge vale in the same location as the old one. That should make it easier to pass smog as well since the location of the purge valve will match the smog diagram.

My time slot also opened up the restoration shop, so for the first time in many months the car rolled out of the garage.



Here's some progress so far ... hood will get re-painted on the underside. You can't see it in this shot, but the top side is all original and in very good shape, so that's been polished. I forgot to get a pic before Roger covered it up, but trust me, it looks sweet.



Here are shots where we're experimenting with different undercoating textures. The yellow is SEM sprayable seam sealer, the primered stuff on the front valance is a water-based coating, and the gray/black stuff next to the yellow SEM is Würth solvent-based coating. We're going to go with the Würth. Note that the glitches in that sample don't come from the coating ... apparently the gun hadn't been completely cleaned, so those glitches are from bits that had been stuck in the gun.





Exciting to see progress!



Last item for today. I have this idea that with the new euro bumpers, the large trunk spoiler from the US car will look out of proportion. One possible remedy is to get rid of the spoiler completely ... but since I definitely DON'T want to damage the existing trunk lid welding the mounting holes shut, my idea is to get a good donor lid from a car without a spoiler (e.g., a 528e), get that painted up black, and mount that on the car. That way I can keep the original trunk unmolested but also get that super-clean euro M5 look. It will likely be very tough to exactly match the black paints, but this should be a relatively cheap experiment. We'll see.

An even better solution would be to find a smaller BMW spoiler that would fit on this car. Any ideas?

[tig]

I dig the spoiler-less look.

You are doing this so right. Big tip of the hat in your direction.

[jhh925]

The paint arrived yesterday. Actual honest-to-god single stage Glasurit 22 Line paint. Very excited to have the new paint be so close to the original.



Drove by the shop to drop the paint off, and got a picture of some more work in progress ... nirvana is a straight rocker.



And one edit to the posts above. I hate my crappy potato pic above of the work I did hooking up the 4-wire O2. The M30-B35 O2 sensor wire bracket is pretty cool, but that pic doesn't show it at all, so here's a new and improved potato pic. The bracket was powdercoated in the last batch.

[jhh925]

I dig the spoiler-less look.

You are doing this so right. Big tip of the hat in your direction.

Thanks. Needless to say, your projects set a pretty high bar. And since my mind is on paint recently, I'll also say that your comments about your experience with Glasurit pushed me to keep looking for a source.

[lizard]

OP: I enjoy reading about all the small stuff. Keep posting!

[Adam W in MN]

I dig the spoiler-less look.

You are doing this so right. Big tip of the hat in your direction.

Thanks. Needless to say, your projects set a pretty high bar. And since my mind is on paint recently, I'll also say that your comments about your experience with Glasurit pushed me to keep looking for a source.

Not sure what the comments were, positive or negative, but I used Glasurit Alpineweiss on my E12 M535i resto and I get lots of compliments on the paint. I am very happy with it.

[jhh925]

Charlie's comments were very positive, along the lines of Glasurit being "tits" and that for car painted in Glasurit, he's "wax that."

Out of curiosity, where did you source your paint, Adam?

And speaking of paint, here are shots of a couple painted items. Front valance:



Underside of hood (I think the amount of orange peel here is pretty good compared to factory, which was the goal):



I also made progress on the "no spoiler" trunk lid. I found what seemed to be a very good trunk lid off of a 528 (so no spoiler holes at all), but when we got it into the shop, we could see that it had two dents that would have to be fixed. I decided to look some more and found a perfect trunk lid off of a 535. Metal work was perfect, but now I had six holes to weld up. The method I used was to fabricate some pressed plugs, then weld the plugs into place. The trunk lid skin is about 1mm and the spoiler mounting holes are 10mm, so I cut a 3/8" hole (about 9.5mm) in a piece of scrap metal that was about 1.2mm thick, then cut donor plugs out of 1mm scrap using a 12mm rotabroach. Then I pressed the flat donor plugs into the 3/8" hole with my 12 ton press using a nub I'd cut off of the end of a 5/16" twist drill. Like so:











I'm not going to claim I'm any kind of an expert welder, but the benefit of this system is that it's pretty easy to hold the plug in the right position, and you're doing less welding (so less heat distortion of the skin) to get the end result. One downside is that you get an edge on the backside where moisture may get in, so you need to be careful to seal it up correctly. Regardless, that I'm aware of, there's no room to do any grinding on the back side anyhow, so even using an un-flanged plug, or using the copper backing method, would likely result in inclusions that could hold moisture.

I ground down the welds (no pics) and the result was that the metal had deformed a bit in the area of the welds (welded area was slightly below the ideal surface as if it had been pressed in a bit). The body shop will work a bit on that and the end result should be a nice clean no-spoiler trunk.

In the "meaningless bling" category, I got my PS reservoir back from the plating shop and put on the new stickers. Mmmmm, yellow ...

[jhh925]

Got the tail panel & rockers schutzed today. That texture should mellow a bit when the primer, sealer, paint, etc. goes on there:



And here's progress on the smooth trunk. I can't tell at all where the welded holes were:

[Philo]

Nice work ! Might consider the Ed Raether steering box post kit. http://www.mwrench.com/download/steeringfix.pdf And, something I failed to do on my S38 build but wish I did, install the oil pump chain tensioner. That is if your block has the hole for the pin. Mine did, not sure about yours.

Great work again, keep it up.

[jhh925]

Nice work ! Might consider the Ed Raether steering box post kit. http://www.mwrench.com/download/steeringfix.pdf And, something I failed to do on my S38 build but wish I did, install the oil pump chain tensioner. That is if your block has the hole for the pin. Mine did, not sure about yours.

Great work again, keep it up.

Thank you!

On the tensioner, yup, got it, though I'd been reassembling the engine roughly in the order that worked on the M30. That didn't work here, so when I discovered that the oil pump chain I'd bought didn't match the oil pump sprocket, I ended up ordering & installing a new sprocket plus the chain tensioner after I'd already put on the head, cam tray, timing chains, etc., which made the oil pump chain & tensioner installation tricky.

On the steering post kit ... I think you're talking about the steering box mounting reinforcement discussed in this thread? I didn't put in the inserted reinforcement, but I did weld in a third "wall" on the mounting bracket to strengthen it up a bunch. Hoping that holds.

[Philo]

OK, glad you did the tensioner. Keep up the great work !

[tig]

On the steering post kit ... I think you're talking about the steering box mounting reinforcement discussed in this thread? I didn't put in the inserted reinforcement, but I did weld in a third "wall" on the mounting bracket to strengthen it up a bunch. Hoping that holds.

This will work fine. The post is a great design and makes the job easy, but adding the other wall should def work too. You are doing great work, sir.

[Zengineer]

Love everything about this thread. Great work! You are too hard on yourself for not being a "professional" - lots of pros turn out work far worse than yours!