Rear Strut Tower Failure

[sandiegomcoupe]

I've been searching through the forum, but I haven't been able to find much information and was hoping someone could help. I have a 1999 m coupe and the left shock absorber ripped away from the frame. Now, this is something that should not happen. The car is stock with the original suspension.

I've been told my a local mechanic that someone he knew was successful in getting BMW North America to make the repairs so I'm trying to gather some more information about this issue to strengthen my case when I talk to them.

Based on my understanding of the subframe/diff issue, this seems unrelated.

[KBH22102]

Does it look like the picture in post 1 of this thread? Rear shock mounts fail at some point. The OEM ones are not that stout. Look at it as an opportunity to upgrade to a higher quality aftermarket mount such as Rogue Engineering

http://forums.bimmerforums.com/forum...&highlight=pos

[sandiegomcoupe]

I took some pictures of the damage.

I'd appreciate any help or info you can offer

[IslandS62]

Wow, its hard to tell what exactly sheared from the photo, which look like it was taken from inside the fender well, but the RSM looks intact in the first. You will need to take apart the rear fender area in the hatch to see what the sheet metal looks like in there. Was it from a single catastrophic impact, or did it fail from fatigue?

[sandiegomcoupe]

It failed suddenly, but there was no impact, catastrophic or other so I'd imagine fatigue was the cause.

It ripped out the sheet metal where it attaches to the frame. It's still mounted to the sheet metal, but that sheet metal is no longer attached to the rest of the car.

[LAWLence]

Interesting. This is precisely why all the aftermarket RSMs have a reinforcement plate.

[JoshS]

This is precisely why BMW specs the installation of a reinforcement plate for the early cars (part number 51718413359) when cars are in for rear shock issues (TSB SI1999-330199).

I'm guessing that the OP's car was built before 10/98.

[Randy Forbes]

First time I've seen damage there. The OE shock mounts are so poor, it's hard to imagine the steel failing before the rubber.

While not an overly easy fix, you shouldn't have too much trouble making a repair; either buy a new wheel well, or have one cut from a salvaged car (Coupe or Rdstr) and have it welded in.

Josh, any chance you have that TSB in a pdf format?

[JoshS]

No, but I have a printout. I could scan it tomorrow. But the basic gist is that some Z3s might have rattling rear shocks. The tech is supposed to remove the shock and insert some washers with rubber/adhesive between the top of the shock and the rest of the hardware. In addition, the tech is to check the inside mounting surface to be sure that it's smooth and if necessary to grind away any crap that's not smooth and repaint with primer.

And finally, the most significant item, cars built before 10/98 should have the reinforcement plate placed on top of the unibody before bolting everything down. It explicitly states that cars after 10/98 already have reinforcement, and that adding the plate is likely to cause noise, so don't do it.

If I don't scan and post by the afternoon, please remind me! Work scanner is way better than the home scanner for documents.

[Randy Forbes]

Thanks, in all this time, I don't ever recall hearing about this.

I keep a bunch of the reinforcement plates on hand, because I used to have to modify the TCK RSMs for the Coupe owners. Both my Rdstrs have plates w/welded bolts in them (99 = GC & 01 TCK).

[Ghery]

Pretty common problem, especially with e36s

Not having reinforcement plates, blown shocks, bad rsms, speed up that damage.

[CaliAgents]

Like Gary said, I've seen this happen a number of times on E36s:

http://forums.bimmerforums.com/forum....php?t=1283649

[Bernie Watkins]

As a possible future Z3 owner, these types of problems tend to make one nervous about buying one. I can't fathom BMW mounting suspension items that take constant abuse, just from everyday driving, and attach them to a unibody without properly reinforcing them. As much as I love the looks of the Z3 and the way it performs and handles, a C5 drop top sounds like a more suitable option that doesn't have these flaws. Am I overreacting to this or what?
Bernie

[Randy Forbes]

As a possible future Z3 owner, these types of problems tend to make one nervous about buying one. I can't fathom BMW mounting suspension items that take constant abuse, just from everyday driving, and attach them to a unibody without properly reinforcing them. As much as I love the looks of the Z3 and the way it performs and handles, a C5 drop top sounds like a more suitable option that doesn't have these flaws. Am I overreacting to this or what?Bernie

Yeah, a little bit

In another few months, we'll have owned our 99 ten (10) years, and I've been a constant presence on BMW Z3 message boards a tiny bit longer than that (research before buying...).

So, to think that this is the first Z3 that I can remember seeing the shock mount poked through the floor, it's not happening every day.

I will add that I spend a fair amount of time around the back end of Z3/Ms, and I am prone to looking for damage. The rear shock tower failure is not widespread.

OT: remember your thread about the guibo? Here's one that was ripe (or rotting on the vine) for replacement...

[JoshS]

Josh, any chance you have that TSB in a pdf format?

Here you go (it is attached to this post.)

Some things to notice:

Page 1: "The production process has been changed to ensure that the body mounting surface is smooth and the mounting surface has been stiffened beginning with 10/98 production."

Page 3: "Do not install the reinforcement plate on cars produced 10/98 and later as it will cause a noise."

Randy, maybe as you come across them, you could take a picture of a pre-10/98 car and a post-10/98 car so we can see exactly what they did?

And BTW, the reinforcement part number shows up as not applicable to Coupes on realoem, although the TSB clearly is. The part number shows up as applicable to M Roadsters, but the TSB does not call them out. My guess is that all of this stuff applies to ALL Z3-based cars, Coupe and Roadster, M and non-M, from before 10/98, but who knows?

I would guess that while the root problem is metal fatigue, the thing that's going to really cause a wholesale failure is a frozen shock that simply transmits all vertical suspension movement straight to that point. A new or worn-out shock will put a lot less load there.

[Vinci]

Wow, impressive. My roadster is a 6/98 build, and it did not have any reinforcement above the RSM. (old photo, from my soft-top replacement guide)

[Randy Forbes]

Here you go (it is attached to this post.)

Some things to notice:

Page 1: "The production process has been changed to ensure that the body mounting surface is smooth and the mounting surface has been stiffened beginning with 10/98 production."

Page 3: "Do not install the reinforcement plate on cars produced 10/98 and later as it will cause a noise."

Randy, maybe as you come across them, you could take a picture of a pre-10/98 car and a post-10/98 car so we can see exactly what they did?

And BTW, the reinforcement part number shows up as not applicable to Coupes on realoem, although the TSB clearly is. The part number shows up as applicable to M Roadsters, but the TSB does not call them out. My guess is that all of this stuff applies to ALL Z3-based cars, Coupe and Roadster, M and non-M, from before 10/98, but who knows?

I would guess that while the root problem is metal fatigue, the thing that's going to really cause a wholesale failure is a frozen shock that simply transmits all vertical suspension movement straight to that point. A new or worn-out shock will put a lot less load there.

Thanks Josh, saved and printed

I've used the same RSM reinforcement on both Coupe & Rdstrs, so you are correct in their fitment.

The trunkfloor is the same for both, obviously Z3s differ from the ///Ms, but no difference between Coupe or Rdstr of the same series.

The Coupe does add a stamping on each side that supports the shock tower, so to speak, but does nothing as far as the top of the tower itself is concerned. These areas are shown in virtually every album for each car I've done the rear end in.

I've only done a handful of cars that would predate 10/98, maybe only a couple, but there was no obvious difference. Maybe now, knowing there was a revision, I'll spot one when I see it?

Wow, impressive. My roadster is a 6/98 build, and it did not have any reinforcement above the RSM. (old photo, from my soft-top replacement guide)

Added Coupe support visible here:



Edit: Note that this RSM was mounted upside down (works great to limit shock travel...) while the opposite side was correct; yay for BMW of Nashville service dept. I corrected this before the car was buttoned back up.



And absent in the Rdstr:



Note that the Coupe's wheelwell support does not address the top of the shock tower, so I'm wondering if the gauge thickness of the stamping (for all variants) was increased when the Coupe went into production?

[Bernie Watkins]

Randy, Thanks again for your help in understanding what we are talking about. I have seen shock tower braces in the rear of ricers that race on weekends and have made several for the front shock towers for C3 Vettes. The Guibo pics look very similar to the "rag" joints for steering joints, although much much stronger! Again my fears are abated. As I realize that these failures are on older cars, and, or cars that are being raced and beat on extensively. At one point in time that would have been me but, although I still drive spiritedly at times, nothing that should cause structural failures we are seeing here. Thanks again for everyone sharing their pictures and experience!
Bernie

[Kyle Anderson]

Here you go (it is attached to this post.)

Thank you so much for that TSB! It solved my rattling after installing new mounts

[alivegy]

I'm going to have the mounts off of my car in the next couple of weeks. I have TC Kline CoilOvers and their RSM's. Should I attach the support plate and gasket while I'm in there? Right now the RSM's are just fastened to the raw metal.

[dwm]

I'm going to have the mounts off of my car in the next couple of weeks. I have TC Kline CoilOvers and their RSM's. Should I attach the support plate and gasket while I'm in there? Right now the RSM's are just fastened to the raw metal.

I've had the Rogue reinforcement plates (and their RSMs) in my car for a long time, and gaskets on both the top and bottom of the sheet metal. No strut tower problems to report with stock suspension, then KW V3, now TCK D/A.

I'm not at all surprised to see this issue. Strut tower and other suspension mount failures are sort of a BMW trademark. E30, E36, Z3, E46, MINI, ...
just be proactive about this particular one and you should be fine.

[alivegy]

yeah i have a pretty strict policy of "replace before it has a chance to fail"

[Jon Shafer]

This problem just occurred in my '99 E36 M3. What a drag... :-(

[john batselas]

hallo bimmers!! Im a bit late to get to know about this issue i know.
I have a question and i would be really happy if anyone hels.. after my e36 95, i got a z3 1.9 2000 facelift.
im about to get hd Meyle RSM's, can i put reinforcement plates on this car or because its after 10/98 i can't.. thank you..

[Shoe Coupe]

No, but I have a printout. I could scan it tomorrow. But the basic gist is that some Z3s might have rattling rear shocks. The tech is supposed to remove the shock and insert some washers with rubber/adhesive between the top of the shock and the rest of the hardware. In addition, the tech is to check the inside mounting surface to be sure that it's smooth and if necessary to grind away any crap that's not smooth and repaint with primer.

And finally, the most significant item, cars built before 10/98 should have the reinforcement plate placed on top of the unibody before bolting everything down. It explicitly states that cars after 10/98 already have reinforcement, and that adding the plate is likely to cause noise, so don't do it.

If I don't scan and post by the afternoon, please remind me! Work scanner is way better than the home scanner for documents.

oh my gosh! is that what that rattle is? it's been driving me crazy for the last year! Every time i go over a bump, it rattles both left and right rear. I thought it was the shock mounts, replaced them but they're still there.

Is it the actual shock that rattles or some part of the mounting/hardware? I put in the Rogue style RSMs with reeinforcements,but didnt use the gaskets on top, only the ones on the bottom but it still rattles...