Z3 @%#@! Rattle

My recently acquired '98 Z3 is coming along nicely but I've got a rattle that's driving me crazy. The sounds appear to originate mainly from the passenger side rear whenever I hit a bump. I thought it was the battery since it wasn't secured yet after fixing that the rattle is still there but the battery was loose and needed hardware anyway. I removed the tool tray and spare tire, no go, still there. While I was under the car I noticed what I think are impact shock absorbers behind the bumper and my Bently service manual refers to them but there's no IPB for the rear bumper so I'm not sure. Both the left and right (impact absorbers I'll call them) are loose, also, I believe the car may have been involved in a rear end collision at some point so here's my question... Do these imact absorbers dislodge or degrade after an accident? How do they work? Do they need to be replaced once they've absorbed an impact or was it just a shoddy repair job? Is there any illustration that shows them as an assembly or better yet an IPB? Has anyone else experienced this problem? Any input would be greatly appreciated. BTW, I checked the E-brake and various areas that were other considerations but I've ruled them out. I also saw a post about "Subframe Vibration Absorbers" in the rear bumper... could these be my problem? Should they be loose and move when I touch them or should they be secured and tight?

Are you sure it's not your rear shock mounts? That's a common cause of rattle in these cars. Aftermarket ones from Rogue Engineering or Ireland Engineering are superior to the OEM ones by quite a bit.

Another possibility is the sway bar.

Originally Posted by Blacklane

Are you sure it's not your rear shock mounts? That's a common cause of rattle in these cars. Aftermarket ones from Rogue Engineering or Ireland Engineering are superior to the OEM ones by quite a bit.

OK. I'm going to replace the rear shocks and rear shock mounts next. Does anyone have the complete list of parts needed to do this? I see there are quite a few options but I'd like to hear what the general consensus is.

That depends on how deep you want to go based on your budget and driving style. If you do a search here* on "shocks," you will get lots of threads ranging from simple Bilstein replacements to full Koni coil-overs.

For the back shocks, all you need are shocks and shock mounts. The job is quite simple really. Or you can go all-out and replace the sway bar bushings, the Rear Trailing Arm Bushings (RTABs), and the subframe bushings.

The subframe bushings should be replaced with polyurethane ones to stiffen the attachment to help avoid the differential mount failure that many Z3s experience. Subframe bushings are not simple, so read-up on it, decide what approach you want to take (subframe tool, shop press, sawzall, cutting torch, etc.).

You can consider polyurethane for the other bushings, since it is harder than rubber, but all of those things move and polyurethane squeaks loudly. Rubber is fine for daily driving and much quieter.

*At the top of the forum page, on the right, is a button called "search this forum."

I was going to say rear shock mounts too. You should check out our little group on facebook
http://www.facebook.com/groups/GardenStateZSCCA/
or our webpage
www.gszscca.org

Our next fix it day will be in Late April or early May.

Al.

Khammack, you're a genius! LOL I have been chasing my little knocking from both sides for months. I already have the Ireland mounts, etc, but never looked at the sway bar. Simple, but effective sugestion. Thanx.

Sent from my SGH-T989 using Bimmer App

I agree with almost all of the above statements. The OEM shock mounts, especially the rubber bushings are awful if they are original to the car.
I replaced mine with the Turner Motorsport billet aluminum ones with new bushings and have had no rattle.

Good luck with it!

Originally Posted by khammack

Another possibility is the sway bar.

Thanks khammack you nailed it. I inspected the shock mounts and didn't see anything that would justify the noise I was hearing so I kept looking and found that 1 end of my sway bar wasn't even connected! Somehow it slipped out of the bushing so it's just floating and colliding with other suspension components whenever I hit a bump. In the repair manual it suggests removing the sway bar and bench mounting the new bushing/mount(s) then reinstalling the assembly. The old bushing is still there but not connected so I'm torn between reinstalling it or going new. I know what I should do but these jobs always end up being harder to do then you thought. Has anyone performed this procedure?

I've not done it but I know some people who have. I'll see if I can get them to chime in if khammack doesn't respond.

OK, the saga continues... I had a BMW mechanic replace the sway bar bushings and mounts as well as the rear shocks, bushings and mounts at a cost of $700. I drove the car home and the rattle (very loud and annoying rattle) was as bad as ever. I really thought I had it this time but no luck. I can't even appreciate the improved suspension because every bump I hit causes such a clatter that it drives me crazy. The lions share of the noise originates in the passenger side rear but nothing seems to be loose under the car. The only thing left that I can think of is to remove the rear bumper and remove the 15 lb counterweights (2) which (if loose) could be heavy enough to cause such a rattle and while its off I can try to see if there is anything else I can find loose. I'd like to know if anyone else has had this problem or heard of this problem. I would really like some help diagnosing this noise.

Hi Again!
Sorry you are still hearing a rattle back there. We're having our next meet on 3/3/13 please feel free to attend and maybe someone can help you out there. PM me for details.

Al.

Originally Posted by russpe

OK, the saga continues... I had a BMW mechanic replace the sway bar bushings and mounts as well as the rear shocks, bushings and mounts at a cost of $700. I drove the car home and the rattle (very loud and annoying rattle) was as bad as ever. I really thought I had it this time but no luck. I can't even appreciate the improved suspension because every bump I hit causes such a clatter that it drives me crazy. The lions share of the noise originates in the passenger side rear but nothing seems to be loose under the car. The only thing left that I can think of is to remove the rear bumper and remove the 15 lb counterweights (2) which (if loose) could be heavy enough to cause such a rattle and while its off I can try to see if there is anything else I can find loose. I'd like to know if anyone else has had this problem or heard of this problem. I would really like some help diagnosing this noise.

I went thought the same problem , diagnosing changing everything as suggested above, so it was left with the counter weights, just removed the bumper and removed those useless weights and the car is so quiet now, the bushing holding it was worn and it was shaking like crazy, my car now feels lighter, no change in handling or vibration.so take them off, it took me 30 min s with simple tools, I bought wrench the torex to take the bumper off.

Originally Posted by atopa2002

I went thought the same problem , diagnosing changing everything as suggested above, so it was left with the counter weights, just removed the bumper and removed those useless weights and the car is so quiet now, the bushing holding it was worn and it was shaking like crazy, my car now feels lighter, no change in handling or vibration.so take them off, it took me 30 min s with simple tools, I bought wrench the torex to take the bumper off.

Wow! I can't tell you how much I appreciate you taking your time to help me out. I was so discouraged when I drove my car (after the work) and that horrible noise was still there. What surprises me is that there is really nothing (until now) that I've been able to find in this truly awesome forum that addresses this problem. I think it's only the 2.8s that have the counter weights but even so wouldn't you think the problem would be more prevalent? Anyway, I'm looking forward to removing the weights but just one question... what is the procedure? Do you have to remove the bumper or other components? Could you just describe the method you used? Thanks again, in advance for your help.

You know, something else you may want to check would be the gas tank dampners.

The straps holding up the gas tank have rubber pads in places. The rubbers fall out, the straps and gas tank rattle.

That would be right behind the seats, and if the passenger side strap was loose. . .

Well I did check the gas tank but not for the rubber insulators, I'll do that thanks. However if you heard this noise you'd agree that it was something further back. If you look at my earlier post you'd see I suspected the counterweights (SWAG) but since there was nothing in the forum I figured it wasn't the culprit. After all I really don't want to do more work then I have to. Now I can't wait till a break in the weather and have at it!

It's very easy,the metal bumper or hard part and the plastic part is help together by two torx bolt,size T50 or 55,jack the rare and look under the car where the bumper is attached to the car,you will see the two bolts at each side holding the bumper to the subframe ,those are the only big bolts you need to take out ,there are two small screws attaching the edge of the bumper to the wheel well plastic,take it out and use your hand to remove the edge of the bumper from the wheel well plastic .you don't have to take out the bumper all the way,the reverse lights wires is still attached,support it with a small chair.

The weights is held to the subframe by a bolt unscrew it then the weights is freed reattached the bumper making sure the side ends get hooked or locked in to the wheel well plastic and then screw the torx bolts back.
It's very easy,I'm not mechanically inclined but it took me just 30mins.
I have had my z3 for a year and its my first car I have worked on my self,changing oil,trans fluid,diff fluid ,fuel filter etc,
John

convertible tops rattle too.

Yes convertible tops rattle and so does everything else on this car :-) But the noise I'm getting is more like bowling balls rolling around in the trunk. As soon as I get a break in the weather I'll be pulling out the counterweights in the bumper and see how things are after that.

I wonder if you are hearing the fuel tank clunk that results from the foam strap pads falling out:

http://www.bimmerfest.com/forums/sho...d.php?t=281932

At least it's easy to inspect.

Originally Posted by smayo964

Khammack, you're a genius! LOL I have been chasing my little knocking from both sides for months. I already have the Ireland mounts, etc, but never looked at the sway bar. Simple, but effective sugestion. Thanx.

Sent from my SGH-T989 using Bimmer App

Is this the front sway bar that you mounted? Thanks.