A metallic "popping" or "snapping" noise - rear suspension

[mightychipster]

Hi, I've exhausted my very limited knowlege of how to resolve my situation so I would like to turn to the good people on here to help me out. Please let me explain. I purchased a 2004 BMW E46 330CI convertible that has only 49,000 on the clock. In the last few months I have experienced what I can only explain as a "popping" or "snapping" noise coming from somewhere in the rear suspension if either:

1. The cars weight shifts i.e. turning a corner or reversing onto my inclined driveway
2. When lifting the rear of the car using a jack
3. The noise comes from both the left and right hand side of the rear

I've replaced the outer upper and lower control arm bushes as well as the rear trailing arm bushes too. I've replaced the shocks and shock mounts and greased the anti roll bar bushes and control arm links. I've had the subframe checked for cracks too but the noise is still there.

Has someone got any experience or suggestions for me please?

I'll try and post either an audio or video clip if I can.

Thanks in advance

[anonymous-user]

I don't know much about BMWs specifically but is this one from the era where the boot floor tears apart?

[mightychipster]

AFAIK the subframe was reinforced on the E46 at some point early 2000 and the convertible apparently has a different subframe and is not prone to the cracks of the other models / earlier versions.

[M4CK 1]

I'd get it upon ramps and get it checked as as mate. I wouldn't chance it.

[peterg1955]

Broken spring(s)? very common on E46s

[996TT02]

Not sure if related

https://www.youtube.com/watch?v=huVgisWett0

[GreenV8S]

mightychipster said:

2. When lifting the rear of the car using a jack

Given that you can reproduce the noise stationary under controlled conditions it ought to be easy to locate the source. Just physically hold on to each joint you suspect might be the source and provoke the noise - you will be able to feel even very small movements.

[E-bmw]

As above if you can replicate it reliably you should be able to find it rather than just changing stuff.

I personally would drop the subframe off its mounts & look VERY closely as the floor would still be my prime suspect, especially as some go inside rather than outside & so can't be seen easily.

[mightychipster]

Thanks for the comments so far, I'm drawn towards the possibility that the coil springs may be showing signs of failure as the root cause. Could this also be known as metal fatigue? I'm thinking springs because when you press down on the rear repeatedly I also get a creaking noise and other than the shock absorber I'm not aware of any other part that "absorbs" movement up and down. Am I right in thinking this?

A very quick search on youtube I found this video (although of a different car and spring set up) that closely matches the creaking and snapping noise, especially at the 10 second mark.

https://www.youtube.com/watch?v=FxIk5-OWfV0

[E-bmw]

As has been said above by me & others, that noise and the fact that you are able to 100% repeat it should be IMMEDIATELY obvious of the cause when you do the same test & "feel" every joint/part until you identify it.

I very much doubt that is spring related as the spring contact doesn't "move" as you compress the suspension, that sounds like dry metal to metal contact between 2 things.

[anonymous-user]

mightychipster said:

AFAIK the subframe was reinforced on the E46 at some point early 2000 and the convertible apparently has a different subframe and is not prone to the cracks of the other models / earlier versions.

This is the one I was thinking of, cracks in the boot floor, quite a mess on this one, someone comments they had similar on a 2006 car also:
https://www.youtube.com/watch?v=fH1MqZ3ncMQ

https://www.pistonheads.com/gassing/topic.asp?h=0&...

Edited by anonymous-user on Sunday 22 July 09:48

[The Wookie]

Probably the Gaz dampers

[E-bmw]

mightychipster said:

AFAIK the subframe was reinforced on the E46 at some point early 2000 and the convertible apparently has a different subframe and is not prone to the cracks of the other models / earlier versions.

The subframe is not the issue, it is the actual boot floor/underbody.

[mightychipster]

So, some good news. I undone the lower bolt on both rear shock absorbers, with the car rear jacked up i then moved the rear wheels laterally in an up and down movement. Hey presto, the culprit was the anti roll bar bushings catching inside the bushings clip. Now both replaced and with a slight layer of grease the noise is gone!

Thanks for all the suggestions

MC