Help - Rear Shock Mount Question

2001 330I 160k original owner

Last year I replaced my rear shocks with Bilstein HD shocks. I reused the top mounts ( I know stupid ). So 1 year later the mount failed an the top of the shock was sticking through the trunk carpet.

Today I went to the dealer and bought the mount, washers, gasket and nuts. It took me about an hour and a half to replace and I torqued every thing to spec after all wheels were down.

I drove the car for 1 hour over some bumpy and twisty roads. Then I heard the loose change sound from the trunk. THE RUBBER IN THE NEW SHOCK MOUNT FAILED.

I'm worried that there is something else that is broken in the suspension that will cause this.

Any suggestions on what went wrong and what I should check?

Also, last week I had to replace the front swing arm on the passenger side (same side) It's the bar that connects the sway bar to strut.

Any help would be highly appreciated. I promise a full write up once resolved.

Thanks.

Sounds like on the front you replaced the sway bar link? Important to use the correct terminology so we'll know what you're talking about.

First especially with HD shocks, I'd never replace the rear shock mounts with oem. Use some aftermarket heavy duty fail safe units with reinforcing plates. Did you use reinforcing plates this time?
At this point we hope your rear shock mount tower may have failed, and that will mean expensive welding repair. You need to take things apart and report back with exactly what you find.
Not to impugn your skills, but are you meticulous about installing things in the correct order, referencing diagrams constantly as you go?

Go to Turner Motorsports for some educational browsing for rear suspension parts.
I bought the $100 mounts

Thanks Stinger for your quick response.

Yes it was the front sway bar link. However both realoem and my receipt list the part as the front swing support.

Before buying the replacement rear shock guide support, I saw many posts that suggested beefier aftermarket replacements, as did you. I planned to replace both at a later date with these parts. However, I needed to get my car on the road and the BMW parts were available immediately.

My real question is: Is there possibly something else wrong or something that I should check for, which caused the new part to fail on the same day. I would hate to do another replacement only to find that it will fail immediately because of something that I overlooked.

Thanks for any help. I will post my findings after this is resolved.

have never heard, nor cannot think of anything that would hasten rear shock mount failure. I'd repeat that I'd want to know immediately what is going on at the top of your tower in terms of shock mount failure, or sheet metal failure. That's what I am afraid of.
You need to start poking your face into the tower area and the rear suspension area to eyeball exactly what is happening before you drive this car.

Rear Shock Mounts (with reinforcement plates)

I installed these last year when I installed my Koni FSDs. Very nice product.

rear shock mount with the shock shaft protruding all the way into the trunk space.
I'm sure this Rogue mount would be robust enough to last as long as the Turner units, but I like the Turner units because the bolts come up from the bottom, making it easy to put the nuts on the top and torque them properly. As I recall, the bolts are captive, so it is a one person job to get them up into place.
I also like the machine turned look of the Al mounts, but admit that no one will ever see these after they are installed. I had fun admiring them before I installed them.

On my previous 5.0L Mustang, I rebuilt the top half of the motor with some new ported/polished aluminum heads and some 1.72 extruded aluminum roller rockers with a beautiful blue anodized coating. Once assembled, the shiney blue atop the black pushrod guideplates sitting on top of virgin aluminum cylinder heads looked like a mechanical work or art. It was a shame to put the (wicked exciting) grey valve covers on them.

What I liked about those Rogue units was the bushing materials, the fact they could be replaced, and the reinforcement plates with the bolts welded to them. Still a one-person job but with the bolts popping through the wheel well instead of up through the trunk.

Can't go wrong with either set, but the Rogue's did come with reinforcement plates.

So I replaced the blown rear shock mount as described. There is one thing that I did not mention. Instead of removing the shock, I retracted the shock and removed the mount from the underside of the car. The body metal where the mount rests looked in perfect condition. The shock appeared to have the proper resistance and move smoothly. I installed the new mount and fed the shock through it. Then the mount blew almost immediately.

Today I decided to take the shock out along with the mount. Once out of the car, I tested the shock by compressing it. At the bottom of its range, it blasted out some oil and did not expand. It was completely shot.

The shock was a Bilstien HD and was 15 months old. I called Bavarian auto (where I purchased the shock). They gave me Bilstien's warranty number. Bilstien has a lifetime warranty. They want me to send in the bad shock. They will inspect it and send out a replacement in a week or so. (Not a very practical policy) Luckily, they did not have any in stock and it would take a month.

I called Bavarian and explained. They would rush ship a replacement along with a heavy duty rear mount (no shipping charge). When Bilstien accepts the return, Bavarian will credit my account.

Now a couple of plugs. I love dealing with Bavarian. Bilstien was somewhat taxing to deal with. The Bilstiens do provide a stiffer ride that I was looking for, but are just too damn loud. Given the choice I would not buy them again.

Thanks for your help. This board is a great resource.

because we learn from other's experiences, so we love to hear how you resolve your situation.
Stock sport suspension is quite stiff enough for most, who would have your same mild regret. BMW gives a good compromise suspension.
Nice follow thru with handling the suppliers to get your car back on the road.

BMW 3-Series Rear Shock Tower Mount Failure


Why It Normally Happens?
There are 2 common reasons for failure of the rear BMW shock tower mounts on the e30, e36, and e46 models. The first reason is metal failure due to rust, corrosion, and load impact caused by severe impacts of pot holes. Severe pot hole impacts will typically cause shocks to bottom out which will eventually fracture the sheet metal. The second reason is incorrect installation or failure to reinstall all the necessary parts.

When replacing rear shock absorbers make certain that you remember to transfer the inverted upper and lower cup washers from your old shock absorbers over to your new shocks before installing the new upper mounts as shown in the image below.


These cup washers are an important part in the assembly, without them the rubber shock mounts will fail very quickly. The rubber shock mounts are designed to soften the impact of a harsh compression of the shock absorber. When the vehicle experiences an extreme impact such as a pot hole in the road the inverted cup washer bottoms out on the outer rim of the shock mount. This washer disperses the impact that would otherwise tear the center out of the rubber mount. The top of the shock has a similar washer to keep the shock from tearing out when the shock is hyper-extended.


Shock Mount Reinforcement Plates
The BMP rear shock tower reinforcement plates will strengthen this inherently weak area of the BMW e30, e36, and e46 models. This mount was originally designed for the Z3 chassis to reinforce the area around the rear shock tower mount bolt holes but has since become a standard add on for most all variations of the BMW 3 Series. For best results we recommend using new mounts, and reinforcement plates on the installation of new rear shocks.

*Sold Individually


Taper-Core Rear Shock Mounts
The BMP Design "Taper-Core" rear shock mounts are a simple fix for a problem that has plagued BMW for many years. BMW's original design relied solely upon the bond between the rubber and tube-steel center core of the rear shock mount. After only a year of wear and fatigue the rubber could break away from the tube steel center core, sending the rear shocks into the rear speaker deck of your Bimmer. To address the problem, an aftermarket supplier developed a taper-core center spacer that would compress the rubber against the outer housing. These are always recommended when replacing your shocks or springs.

*Sold Individually


Billet Aluminum/Urethane Rear Shock Mounts
The BMP design rear shock mounts are an excellent addition to a high performance suspension kit. The BMP Design Rear Shock Tower Mounts use 60 durometer urethane cast-in bushings that permit the mount to be used on street performance vehicles or the weekend race car, without the harsh ride and damaging effects of solid steel racing mounts. Constructed of 6061-T6 anodized billet aluminum.

*Each kit includes 2 complete urethane mounts, neoprene gaskets, and custom upper re-enforcement plates.