2009 Z4 s35i metallic clunk in rear end

[SimonW]

I have a 2 yr old Z4 s35i DCT, done 11k miles , no harsh treatment, mostly motorway driving. Car runs really well but about 2 months ago it developed a metallic clang in the drivers-side rear end that was audible when hitting a pothole or when chassis was under "stress" eg when reversing down a slope out of my driveway and turning the wheel at the same time. Quite an ugly sound - almost like something snapping !

I took the car back to BMW - dealer has had car for nearly a month now and after thinking it was a mechanical problem (and fitting a new driveshaft and differential !), they can not diagnose the problem. They are now in the process of dismantling the rear suspension to "visually inspect it for faults" ! ie they've got no idea.

I thought it was a suspension problem at the outset, but am no closer to finding out and am getting worried .... does anyone have any ideas ??

 

[Wondermike]

Are you sure it isn't the roof clunking together - my SLK used to do it in just the circumstances you describe - a down- or up-hill tight slow turn.

Lubricate the roof seals with Gummi Pflege or get the dealer to do it.

 

[SimonW]

Yep - i did think of that initially, but the noise is definitely from beneath the passenger compartment. Also, and worryingly, the noise is worse since the dealer fitted the new diff and driveshaft !

 

[Wizas]

Is the rear height the same on both sides? If not you could have a broken spring. This is a very common problem with BMWs. I know that the garage has had the car but .......... When I bought my car it was given a new MOT by the dealer (non BMW). When I got home and inspected the car I found that the tip of one of the rear springs had broken. The broken section was still there rattling at the base of the spring. It was badly rusted. So much for the MOT!

 

[SimonW]

Thanks for the thought... but the car looks fine - ie level all round. i spoke with the dealer this morning for the latest update. They have stripped the rear suspension and subframe and ordered a new set to be fitted this week. They hope that will do it, but they couldnt see anything wrong (visually) with the existing set so theyre still shooting in the dark really.

Not good. Apparently they have consulted BMW technical dept but no joy. BMW will send a guy out to observe the noise if the new suspension doesnt fix it.

 

[Wondermike]

Interesting. Keep us posted with the fix please

 

[dan bmw]

Any update on this issue?
I am having the same problem.

 

[Maniac]

I get the same. Like a metallic clunk or pop. In the bimmerpost forums quite a few have reported this. General consensus is either.. Floating rear brakes or dry rear anti roll (sway) bar bushings.. Even drive shaft slack.

I seem to get the noise only when driving over sunken manhole covers. It's been inspected and no fault found so while irritating, I've not pursued it further.

 

[TitanTim]

Didn't someone else have this problem cant remember who, Bigendbob maybe. It was found to be fault on the rear suspension, might be worth doing a search.

Tim.

 

[Maniac]

Didn't someone else have this problem cant remember who, Bigendbob maybe. It was found to be fault on the rear suspension, might be worth doing a search.

Tim.

It was bigendbob and it was the anti roll bar bushes that were noisy/sticking. Not sure if that's the pop sound I get but not worried about it either.

 

[bigendbob]

Yep, drove me nuts, a clunk when slow speed turning. Turned out to be the anti roll bar bushes. I did try to get them off, one came free but the other was behind the exhaust, so just gave up as i had it booked at BMW Garage.
They finally removed and greased bushes, and the noise went away.

If you can get them off, just apply some copper grease to them where they contact the bar. I think the rubber just gets stuck to the bar stopping it from flexing.

 

[dan bmw]

Interesting. I'll have to take a look at those bushings.
I have a clunk when turning but also a nasty cracking/popping noise
when slowly turning in reverse. Nothing is loose.

 

[bigendbob]

If i slow turn in reverse, i notice the front wheels scrub and jump a bit, as though the geometry of the wheels can't cope with reversing.

 

[Maniac]

If i slow turn in reverse, i notice the front wheels scrub and jump a bit, as though the geometry of the wheels can't cope with reversing.

Normal for wide tyres/this suspension set up.

 

[Maniac]

Interestingly I've always considered the battery cover in the boot a bit of a BMW oversight. It just floats there with no padding or securing mechanism. I've now put two self tappers through the battery lid that fixes it securely to the boot floor (popped a small screwdriver in the lockable compartment next to it). Now the cover is secured the knock from the back of the car seems to have gone?

 

[bigendbob]

I've noticed the clunk starting to come back again. When i turn 90 left or right, but not yet as previous when going over speed humps or reversing.
Greasing the anti roll bar bushes cured the problem previously. But might need a more long term solution. Wonder if this is a situation requiring some polyurethane bushes? The rubber bushes just might be gripping the bar too much.
When reversing at full lock my front wheel on the outside of the turn jumps or kicks as if i have driven over a small branch or stone.

 

[Maniac]

Oddly enough I had a nice BOING from the back going over a speed hump last night (at 15mph). I've checked my suspension when having tyres replaced, having heard this once before, and all looks ok. I'm guessing its the anti-roll bar sticking too. Its rare I hear it though.

 

[bigendbob]

Well definitly back today, every turn seemed to give a clunk. I almost wait in anticipation. Drives me nuts. I assume the grease has probably migrated away from the rubber bushes.
When i first investigated the problem i resorted to climbing into the boot whilst a friend drove the car. Theres a definite bump noise on the lower boot floor right hand side. I have even recorded the noise on a camera left in the boot! Almost sounds like someone hitting the underside with a soft hammer.
Best way to replicate the probelm is to drive the nearside wheels up the curb stones on the slopping bit of a dropped pavement to a drive way. As the one side is lifted and the rear lifts the clunk occurs.This is what i used when showing the BMW tech guy the last time i visited.
Problem was they spent all day on it till they finally greased the anti roll bar bushes. Seems to be a sticking plaster cure and not solving the real problem.

 

[Maniac]

New bushes, or louder HiFi I'd say...

 

[bigendbob]

Looking at these might give'm a go;
http://www.ebay.co.uk/itm/BMW-Z4-E89-Rear-Anti-Roll-Sway-Stabilizer-Bar-Bush-Kit-SuperPro-/230928319497?pt=UK_CarsParts_Vehicles_CarParts_SM&fits=Plat_Gen%3AE89&hash=item35c466840
Interestingly it says they come with grease, yet i'm sure the originals are rubber, one assumes normally they wouldn't need grease.