Rear sway bar issue - what to look for

[dekaliber]

I'm starting to notice the "pop" from the right rear that I suspect to be the common rear sway bar issue that others have experienced. It's extremely intermittent and I started noticing it maybe a week ago. I am unable to reproduce it reliably, but it does happen enough that I can almost certainly say it's from the car, and not what I'm driving over. Also, it only seem to happen at low speeds.

I'm about to take off the wheel to check, but I'm not exactly sure what I should be looking for. Anyone have a picture or could point me in the right direction? I searched and didn't really find much.

[inTgr8r]

You will see better from the back of the car.
The sway bar mounts can be see up behind the exhaust cans.
They are a U clamp with two bolts.

RealOEM

[dekaliber]

Well, took off the back wheels and took a look. Nothing seemed loose. The u-clamp mounts were fine.



On the right side, there seemed to be a slight gap at the top end of the stabilizer beam (#6 here) that connects the sway bar to the upper wishbone (#12 here), but when I tried to torque the nut it didn't seem loose. Granted I didn't have an open-end wrench so I fudged it with an adjustable, so I wasn't able to get a solid grip with much leverage. I believe another member here posted a similar pic, also of the right rear: http://www.zpost.com/forums/showthre...=rear+sway+bar (post #9).



Thoughts? Could it be an issue with the shocks? The pop/clunk seems to be happening more often now -- seemingly only at low speeds and only when going over some bumps (but not all), and seemingly more so during turns.

[Blind32]

I'm sure you've already checked this but, is there anything in your trunk? or in your battery/m mobility kit that might be rolling around?

[dekaliber]

Originally Posted by Blind32

I'm sure you've already checked this but, is there anything in your trunk? or in your battery/m mobility kit that might be rolling around?

I actually hadn't, but I did take a look a few days ago and it looked like there were two loose plastic rivets -- one holding the bottom carpet to the mobility kit frame and one holding part of the right side carpet. I fastened both pretty tight and made sure there wasn't anything that could be moving in there.

I thought that might have resolved it, but nope. Still get an occasional clunk from back there, and seems to be isolated to the passenger side. Happens ever time I drive, but it's pretty hard to reproduce.

Could it be something to do with the rear shocks/springs? And what would I check for? I don't really get the feeling that there's anything amiss with the suspension. Took it up to 120 mph on a sweeping right on-ramp and felt totally stable (granted, most of the stress was on the left side of the car).

Might bring it in to the dealer, but I'm not confident that they'll be able to identify the problem since it does happen so intermittently.

[thekurgan]

For some new vehicles, there was an audible pop from the diff unit, but that went away after break-in. Do you get this crawling up a driveway or curb?

[dekaliber]

Originally Posted by thekurgan

Do you get this crawling up a driveway or curb?

Car has about 17K miles, and I've owned it since 15.5K. Just started happening a few weeks ago. I do tend to get it with grade/elevation changes, though not always at the same place twice. I'm pretty sure sound is coming from rear right.

I do have the OEM strut brace installed, if that matters at all, but did not start happening right after. I can't think of anything (bad potholes, bottoming out, etc.) that might have precipitated it.

[jragan]

The sway bar issue is usually accompanied by a groaning with the popping. I'm wondering if perhaps you have e-brake issue... Have you changed to aftermarket rear brake pads?--And if so, could it just be pad knock-back due to not exact fitment?

[gnx]

Have a look at this

http://www.zpost.com/forums/showthread.php?t=75418

[lnc2bldr]

Are the braces torqued correctly?
I had a situation where sometimes would get a pop, sometimes a creak, sometimes both when driving over an elevation change, more dramatic when going over a curb one wheel at a time (body flexing a little more).

[dekaliber]

Originally Posted by jragan

The sway bar issue is usually accompanied by a groaning with the popping. I'm wondering if perhaps you have e-brake issue... Have you changed to aftermarket rear brake pads?--And if so, could it just be pad knock-back due to not exact fitment?

Definitely no groaning here. I suspected an e-brake issue as well as I've noticed a pretty loud clunking sound some mornings as I'm first backing out of my garage. Could I have messed something up from jacking up the car with the e-brake engaged? Last time I jacked up the front corners of the car, I noticed that the rear brake would kind of creak and pop as I lowered it. I've since switched to using wheel chocks.

Originally Posted by gxanthop

Have a look at this

http://www.zpost.com/forums/showthread.php?t=75418

Good find! I'll take a look at that. I guess I'm wondering why the OP didn't simply use adhesive to re-fasten the pad. wrapping everything up with tape looks a little...well, "aftermarket."

Originally Posted by lnc2bldr

Are the braces torqued correctly?
I had a situation where sometimes would get a pop, sometimes a creak, sometimes both when driving over an elevation change, more dramatic when going over a curb one wheel at a time (body flexing a little more).

Do you mean the front firewall braces or the rear sway bar? I didn't really have enough clearance or the right tools to get a torque wrench back there. Haven't checked the front braces but I would suspect the sound would be coming from the front in that case...

[RBull]

Originally Posted by dekaliber

Definitely no groaning here. I suspected an e-brake issue as well as I've noticed a pretty loud clunking sound some mornings as I'm first backing out of my garage. Could I have messed something up from jacking up the car with the e-brake engaged? Last time I jacked up the front corners of the car, I noticed that the rear brake would kind of creak and pop as I lowered it. I've since switched to using wheel chocks.



Good find! I'll take a look at that. I guess I'm wondering why the OP didn't simply use adhesive to re-fasten the pad. wrapping everything up with tape looks a little...well, "aftermarket."



Do you mean the front firewall braces or the rear sway bar? I didn't really have enough clearance or the right tools to get a torque wrench back there. Haven't checked the front braces but I would suspect the sound would be coming from the front in that case...

I've seen a post or two where that was the problem someone had and they also thought it was somewhere else. Apparently these cars need to have the front braces regularly tightened.

[lnc2bldr]

I'm talking about the braces that run from the rear differential to in front of each rear wheel. My car had the sound coming from the back trunk area like you describe that went away after torquing these down. I assume the M's have these braces as well?

[blender]

Originally Posted by lnc2bldr

I'm talking about the braces that run from the rear differential to in front of each rear wheel. My car had the sound coming from the back trunk area like you describe that went away after torquing these down. I assume the M's have these braces as well?

Yes they do. Good idea, can't hurt to torque them to spec.

[blender]

Also - the bushings may just be dry inside. You can try lubricating them with some high quality grease[ 3M makes a pure silicon grease] or teflon grease. I would not recommend a spray as they don't last very long.

[dekaliber]

Thanks for the suggestions, folks. I left the car at the dealer yesterday and hope that they'll be able to recreate the problem today. It happened twice during an initial ride with the SA, but then the next day I took a ride with the tech who would be looking at the car and couldn't get it to happen. I did pull the parking brake while coasting to a stop from low speed a few times as someone suggested in another post, so I wonder if that might have fixed it. They suggested I just leave the car overnight and have them take a ride in the morning. Seems like that's when it's most noticeable for me.

jragan - forgot to mention, all brakes are stock.

rclem05 - if the bushings were dry, wouldn't the sound be a more constant rubbing?

[dekaliber]

Originally Posted by rclem05

Yes they do. Good idea, can't hurt to torque them to spec.

Anyone off hand know what the torque spec for these bolts are? They don't *look* loose, but it's hard to tell.

The dealership could not reproduce the issue on a few drives, but did a complimentary inspection and found everything to be sound. Interestingly enough, that day the sound seemed to be entirely absent, but now it's back with some regularity. Still impossible to reproduce reliably. Often happens during bumps/turns but not always. I'm going to take a look at the top of the strut housing inside the trunk later on.

[thekurgan]

Originally Posted by dekaliber

Anyone off hand know what the torque spec for these bolts are? They don't *look* loose, but it's hard to tell.

The dealership could not reproduce the issue on a few drives, but did a complimentary inspection and found everything to be sound. Interestingly enough, that day the sound seemed to be entirely absent, but now it's back with some regularity. Still impossible to reproduce reliably. Often happens during bumps/turns but not always. I'm going to take a look at the top of the strut housing inside the trunk later on.

22nm from what I remember. Several guys have invested in the Nord Lock

http://www.nord-lock.com/default.asp?url=1.16.37

So they don't come loose as easily.

[lnc2bldr]

Originally Posted by dekaliber

Anyone off hand know what the torque spec for these bolts are? They don't *look* loose, but it's hard to tell.

The dealership could not reproduce the issue on a few drives, but did a complimentary inspection and found everything to be sound. Interestingly enough, that day the sound seemed to be entirely absent, but now it's back with some regularity. Still impossible to reproduce reliably. Often happens during bumps/turns but not always. I'm going to take a look at the top of the strut housing inside the trunk later on.

Mine was making the noise regularly whenever you would expect the body to flex. I checked the bolts and they were tight. I just grabbed my 18 inch braker bar and hit them to get a little more, possibly a sixteenth of a turn more. I didn't have much hope that it was fixed but to my surprise the noise was no more. It has not returned and I did that last December.