Folks,

Please help me, I am extremely frustrated with this noise. I'm hearing a loud hammering sound coming from the right rear that sounds like metal hitting metal. There are often rapid hits like a jackhammer or a woodpecker. I have been working on this for weeks now. I am so tired of getting this car up and off of jack stands! I have read many posts, watched many videos and tried everything I've seen and everything I can think of, so if you're going to suggest some searching, please don't respond.

My car's suspension isn't lowered, and the springs appear to be in good shape.

Here's everything I have done so far:
Had a thunk, had the shop to install new struts (koni yellows not including springs) the thunk didn't go away.
Re-did all of the suspension bushings, including a new heavier sway bar (middle stiffness setting,) and sway bar end links. Powerflex polyurethane all around. Thunk persisted.
It's been probably three years and thousands of miles since the struts were installed at this point. The thunk was tolerable, and only happened on really rough roads.
Got around to replacing the bushings at the tops of the struts. Thunk persisted.
Thunk turned into a terrible metal on metal sound. I took the strut assembly apart and realized that I hadn't torqued the top nut, and it had come undone. Adjustment pin on the top of the strut is hosed, but since it's in the enclosed int the top of the strut tower, not too worried about that. The cup that the bushing sits into is damaged a little. Pulled the left rear and made sure I torqued that one as well.
Now instead of a thunk, I get a terrible metal on metal rapping/hammering sound with bumps in the road.
All of the suspension bolts are tight, subframe is tight, sway bar is tight and the bushings are good. There is play in the exhaust, but I can't make it hit anything solid by pushing it around.
Disassembled the interior, removed the bumper and bumper bar, took the wheel liners out, looking for anything that could be loose and making that noise. No Joy.
Replaced the sway bar links, no change.
Took the strut assembly apart and made sure the spring seat wasn't worn through, and that the spring is facing the same way as the left side setup that isn't making noise. The two colored paint marks on the spring are roughly facing inward. (clearly grasping at straws here) Rapping persists.

When I had the strut assembly apart, I made sure I could move the strut in and out. I could do that, though I was surprised that it was relatively easy. I've had shocks in the past that took serious work to compress once you set them free. This wasn't that hard, and didn't push hard/quickly to get back to extension. I didn't specifically test for it, but it didn't obviously have any lateral movement possible, or look like it wasn't straight. Also, no leaks.

I don't have a good way to get a torque wrench on the top of that strut. I'm just getting it as tight as I reasonably can with a small (8 mm?) wrench on the top and the 19mm wrench on the nut. Think about as much torque as you can put into a 8mm wrench safely.

I have a new pair of koni yellows in the box ready to go, but before I make the $360 commitment and open those boxes, I want to make sure I'm not missing something. Do you think those struts are shot? Have you had a bad strut make a metal on metal hammering noise?

Also, is having the top nut too tight a potential problem, besides over torquing and damaging the strut? It seems like if it's not well seated, the nut is going to ride off and repeat the problem.

Thanks for reading my saga, and I am looking forward to your wise advice.

Cheers,
Duane

 

heatshield above the exhaust possibly

 

Rear hatch?

I would say end links loose but I think you covered that.

strut mounts, bearings, ebrake cables? now I’m just listing ****

 

First, thanks for the quick replies. It's much appreciated.

Exhaust shield: It seems like the sound is too loud to be anything from the shield, but I'll check.
Hatch: I drove the car down the street with the hatch open. Same sounds.

Cheers,
Duane

 

I feel like we have the same noise.

kinda like a pool ball dropping on a pool table?

 

Have you had the car up on a drive-on lift or lowered the car's rear tires onto big blocks of wood so that you can see what's happening with normal load on the rear suspension? It could be something so simple as a`rear exhaust hanger or a drop-link too close to a suspension component. Are your rear sway bar bushings worn? If so, the sway bar could be shifting side to side.

 

I've had a noise in the back for quite some time now and it's the carrier that got machined by the pads after 15 years and 200,000 km of driving. It goes Woody Woodpecker, but it will stop as soon as I touch the brakes just a little bit since it's putting pressure on the pads so they stop listening to House of Pain's hit song. That crappy design with no pad support plates means that the pads are rubbing against the carrier itself. I lived with that noise knowing that I'd get around to replacing everything at some point. I ended up swapping the front with the R56S to do the Poor Man's JCW brakes, but also bought the rear to do the conversion since I already need a caliper anyway (hand brake mechanism seizing) AND I really... but really wanted to ditch the stupid euro design and the conversion allows me to get proper brakes with pad support plates (like Toyota, etc) so the pads aren't eating the carrier over time.

I don't know if pressing on the brakes make it stop, but I'd look into it. A bit of play from the pads in the carrier is normal, but a lot isn't. On mine, I can actually see the wear on the carrier, so even new pads will jump around simply from the rotor dragging them a bit. I'm not saying that it's your problem, but if that's it, good. If not, my thoughts and prayers are with you!

 

Same thing was happening on my '04. I had replaced the shocks when I rebuilt the rear struts (new everything except the springs) but could not find the clunk. Ended up replacing the rears with complete new assemblies and the noise went away. Still don't understand why the previous set was rattling.

 

Check the upper spring perches on the strut assembly. The one side on my R53 had to be replaced because the strut rod had punched thru the steel.

 

Are you sure it's not just the sound of unburned fuel reaching the exhaust? It basically detonates there and makes those thunk sounds. It's not a problem; It's common in sports cars.

 

Wait, wHaT?!?! How is that possible? That could never happen in a finely engineered, BMW built car!

 

Solved it!

First of all, thank you for all of your suggestions. None of them ended being the problem, but they were helpful in diagnosis. Oddly, I had never tried just opening the hatch and bouncing on the back bumper. I had always been in the driver seat, trying to guess where the sound was coming from.

Here's the smoking gun.


Hopefully you can see from this picture that the top of my strut is hitting the inside of the frame rail. thus, when I hit bumps, it sounded like someone with a hammer hitting the body.

I took the strut assembly apart, trying to figure out how to make the top of the strut shorter. I flipped over the concave washer, no joy. I really needed a spacer of some sort, and likely not something that I was going to be able to find at my true value. At this point I opened one of my new struts, and looked at the hardware that came with it. I noticed there was a washer/spacer that wasn't part of my assembly:



This was the key piece I was missing. There are two possibilities. One, that whoever installed the struts for me at the shop accidentally forgot this piece, or two, that when I replaced the bushings with powerflex bushings, I neglected to put it back in place. I kind of doubt that it was the second possibility, as I had a knock/rattle before I did the bushings, and I wouldn't have had any reason to take that washer off of the strut when doing the bushing work. I think I would have noticed the extra part, unless it fell to the floor of my admittedly messy shop.

Regardless, I didn't have a washer to put on the old strut, and I was more than $380 worth of frustrated with this effort, so now that I KNEW I had a solution, I was ok with spending the money on the new struts.

Thank goodness that challenge is over. I think I can pull a pair of rear struts off and put them on in about 40 minutes now, that I've done it so many times.

Thanks again for your feedback everyone, much appreciated!

Cheers,
Duane

 

I have a similar noise and it came from the right rear shock top bushing. It was crushed flat. Replaced both shocks with good silicon bushings. Noise gone!