"Clunk" from the Trunk Funk

[Ogopogo]

Well, it seems if it's not one thing, it's another with this rig! I recently finished changing out the Valley Pan/Valve Cover gaskets, and Spark Plugs, with fingers crossed that would be it for a while. No such luck.

It seems to be all good under the hood, but now I have a very solid, and audible "Clunk" sound upon sudden braking and acceleration. Looking first at what was messed with last: I made certain that the spare tire, jack, etc, were all properly fastened down. Didn't help. Removed the spare tire from the trunk well. Nope. Put a towel between the glass and the tail gate to make sure it wasn't originating from the hatch. No dice.

I'm able to create the sound quite easily at low speed by letting it roll, and stomping on the brake. There is a very brief pause between hitting the brakes and hearing the clunk. I enlisted my trusty mechanic neighbour, to have a listen/feel. He had me step on the brake and the gas at the same time to check the differential. No apparent problem there. He then had me roll back a few feet at a time and stomp the brake while his hand was on the trailer hitch, and he could feel a very definite vibration. With that, I got under it, and made sure all of the fasteners on the hitch were tight (none felt loose). Clunk still present.

In summary, the sound doesn't seem to be that sensitive to bumps (up/down) but more to front/back. It's a lot like the noise you get when towing a trailer. The relsuting noise from a little slack in the ball mount/hitch pin upon acceleration and deceleration, and seemingly originating from the same area.

Any insight appreciated!

[X5SND]

It started all of a sudden? Whats your situation suspension wise in the rear?

[Ogopogo]

It seems to have appeared out of the blue. That's why I thought that it might be related to me pulling stuff (spare tire, etc.) out of the trunk well while doing the VPG, but that doesn't seem to be the case.

Suspension is bone stock. Had an alignment done about a month ago, when I had the thrust arm bushings done. The clunking started just a few days ago, for no obvious reason. I was under it today, while doing an oil change, and nothing really appeared out of sorts.

Could it be something in the drive line, flex discs? slip yoke? I don't think it's transmission related, but I have been wrong before.

[absentmathis]

Battery mounts tight? The little pause you mention makes it sound like something shifting to me, rather than a worn part of some kind.

[Ogopogo]

I didn't actually check the battery mounts (yet), I didn't mess with the battery during the VPG job other than to disconnect the negative terminal. I do think you are correct in that it feels/sounds like something loose and shifting, something fairly heavy as well.

I did recently noticed that the lower portion of the back seat was not properly clipped in to the retaining points, so I fastened it in, but can't imagine that is the source of my current issue. The investigation continues...

[electricalserv x5]

try checking to rear wiper in the window,these brake and hang in place for some time.
next check the rear trunk latch lock................see if the latch in the hatch is lose, both are easy repairs............

[jlam86]

does it sound like metal against metal kind of a clunk?

i have an e70 and one of the strut bolts on the rear tailgate was scraping up against the bolt of the bump stop for the tail gate. so you get this kind of a metal to metal clunk. it was so F!cking annoying. I ended up taking out the factory bolt and got a lower profile head one. solved the problem.