Help! Rattle in LR suspension... can't find it.

[topnotchrally]

I have a 99 Z3 2.8 manual roadster. 140k kms.
It's a great car, fastastic to drive. I've recently replaced all the shocks with Bilstein B6 as well as the front control arms with HD units and the upper strut bushings/bearing.

This week it has developed a nasty hollow rattle from the left rear suspension. It's most obvious at very low speed, like rolling on my gravel drive, it's most obvious. It cant' be heard at road speed over the road noise.
It's definitely related to the up/down movement of the wheel. I've jacked it up and looked/pushed/pulled, I can't find any play. I even swapped the shocks left<->right, the noise is still on the left.
My thinking is it must be the trailing arm bushings or subframe bushings, both are difficult to see/push/pull under the car.

What do you all think?
Thanks.

 

[Scooblitz]

Hello

It could very well be the trailing/subframe bushes. My guess would be subframe bushes if you have checked the struts and are happy that its all right and tight.

The subframe bushes collapse from the inside and end up resting on the plates bolted to the side of the chassis. There could be an inch or so of linear movement where the whole subframe is moving and would certainly do so on bumpy roads.

Have a peak, take some photos and post them up but I am confident they will need replaced as pretty much all z3s need them done.

Its a subframe off job to sort it but there is plenty of help and guidance on the forum to assist.

 

[Duncodin]

It could be anything - even things unrelated to suspension. First thing that springs to mind is the spare wheel carrier. That can make a hell of a racket if not bolted in tight.

My sub frame bushes were shot. Didn't rattle but made the whole car wobble with a thud going over potholes. I changed mine without removing the sub frame following info I found on the forum.

 

[BillyB]

See if you can get in on a ramp or over a pit as when its jacked up you will have taken up any slack items . Check out rollbar and drop links they are good for a rattle. Try your brakes and hand brake just a little as you move and see if that changes anything. Also check petrol tank straps, that's where I had a rattle. Good luck .

 

[SV8Predator]

I had a really annoying rattle, very similar to the one you describe. I checked everything, spare wheel carrier included. But I just couldn't pinpoint it. Annoyed me for a couple of years.

Sorted it this summer.

It turned out to be the rear inner brake pad rattling in the caliper (RH side). The LH one was solid but this one was rattling away.

 

[topnotchrally]

Fixed it. Thanks to everyone for their input, special thanks to BillyB, it was the gas tank strap! I never would have looked at that. I don't understand how anything would have changed recently, but where the trap hooks at the back it was just a bit loose and would 'clunk' as I pushed it up and down... sounded so familiar. I put a couple cable ties on it and now, no more rattle. That's a relief. (see below)

I had a good look at the trailing arm and subframe bushings. I put a jack under the subframe and there seemed to be virtually no play when I jacked up the car by the subframe. I pried on the trailing arm bushing and they also had no obvious play. at 140k kms (87k miles) it be a good idea to replace so perhaps I'll buy the parts so I have them when the need arrives, or I feel like doing it.
Here's a load of photos of the bushings, for the very curious (or helpful?) PHOTOS