[BMWM.D.]

What I hear in my car and what I heard in the other one yesterday definitely isn’t from the ASD/stereo. Another technician and I (both with 20 years BMW experience chasing this type of problem) took turns laying down in the trunk while the other drove. It’s from under the car somewhere in the rear.

The easiest way to reproduce it is: fold down the rear seats, find a bumpy yet smooth (ie well paved; not gritty and rough), and cruise along at a steady 10 mph. It’ll only do it on certain roads. You’ll hear nothing on a very smooth road, but you’ll get a lot of repeatable and frequent hollow knock type sounds over the bumpy ones.

I guess I can’t say every M240i does it, but since my car (600 miles) and the one I drove yesterday (5 miles) do it, I’m guessing it’s at least a very common thing.

[mechman]

Originally Posted by BMWM.D.

What I hear in my car and what I heard in the other one yesterday definitely isn’t from the ASD/stereo. Another technician and I (both with 20 years BMW experience chasing this type of problem) took turns laying down in the trunk while the other drove. It’s from under the car somewhere in the rear.

The easiest way to reproduce it is: fold down the rear seats, find a bumpy yet smooth (ie well paved; not gritty and rough), and cruise along at a steady 10 mph. It’ll only do it on certain roads. You’ll hear nothing on a very smooth road, but you’ll get a lot of repeatable and frequent hollow knock type sounds over the bumpy ones.

I guess I can’t say every M240i does it, but since my car (600 miles) and the one I drove yesterday (5 miles) do it, I’m guessing it’s at least a very common thing.

Could it be the frequency isolator mounted in the center of the rear subframe causing that weird noise trying to isolate all the other noises in the cabin? It might be that at low speeds the noise from the isolator is louder than all the other possible noises in the cabin.

You could try disconnecting it (if possible) to see if the noise goes away

[BMWM.D.]

Originally Posted by mechman

Could it be the frequency isolator mounted in the center of the rear subframe causing that weird noise trying to isolate all the other noises in the cabin? It might be that at low speeds the noise from the isolator is louder than all the other possible noises in the cabin.

You could try disconnecting it (if possible) to see if the noise goes away

I was looking at that the last time it was in the air. It should be easy to remove, though I really don’t know if I’ll devote much time or effort at this point. Based on the feedback from other owners here as well as my experience with the other car, it’s likely a “normal” design characteristic. Could even be something like a software glitch causing the adaptive shocks to make noise. F30s had a similar issue.

I’m hoping it’s something BMW knows about and is investigating. I think we have a chassis ear setup somewhere that I might play around with. Maybe I can isolate it. Otherwise, I think I’m keeping the radio on and trying to ignore it.

[hermiti]

I'm pretty sure mine was the toe hook, it was only partially held down by one of the two Velcro pieces. Haven't really noticed it since I fixed it.

[xcelir8bmw]

I now realize that I can make a thump by going over larger speed bumps in addition to shifting from gear to gear hard and no it is not exhaust sound it definitely is a thump and no it is not the tow hook.

[MattM240eye]

Originally Posted by xcelir8bmw

I now realize that I can make a thump by going over larger speed bumps in addition to shifting from gear to gear hard and no it is not exhaust sound it definitely is a thump and no it is not the tow hook.

Yup, it seems like it's a suspension thing, not saying there is a functional problem, but maybe a design issue, maybe lacking padding or something..

[SN1P3]

Everyone who has the "thump", did you have RAM installed at the port or somewhere other than factory?

Trying to determine if thump is related to RAM install.

[BMWM.D.]

Originally Posted by SN1P3

Everyone who has the "thump", did you have RAM installed at the port or somewhere other than factory?

Trying to determine if thump is related to RAM install.

My car had the RAM installed at the port. I still haven’t pulled the left trunk liner to QC their work, but I don’t think it’s coming from something loose inside the trunk area.

Like I mentioned though, whoever did my car did crap work. Just from a quick glance, they broke one of the plastic nuts for the liner, and left another plastic rivet clip out. Doesn’t instill much confidence in the quality of work they did behind the liner.

[Caerus]

Any update on this phenomenon? I picked up my car last week and there is an annoying thumping sound in the rear as you guys have explained and have been trouble shooting. Thanks.

[SN1P3]

Originally Posted by Caerus

Any update on this phenomenon? I picked up my car last week and there is an annoying thumping sound in the rear as you guys have explained and have been trouble shooting. Thanks.

I think we're all just living with it. It doesn't really bother me especially since I know it's something found in most if not all.

[xcelir8bmw]

Yeah just living with it.

[Rdurty2]

All these complaints and no one takes their car to the dealer to have it looked at?

[Caerus]

When I read through the whole thread, there were some that did go to the dealership with varying degrees of results. Also, one guy here works as a technician at a BMW dealership and has to his disposal a wealth of knowledge and is trying to trouble shoot the problem. I just took delivery of mine last week and want to try and understand the problem more before I go to the dealership. My M240i is the first at my dealership and if I took it in for this problem, they would be puzzled by it and have to start the whole trouble shooting process over. So hopefully some here have further information.

[ReallyRadams]

I’ve also heard the thump over bumpy roads from the rear. I have a 230i nothing non sport. Mine was built Jan 2022 and has 1,100 miles.

[kkgriss]

Originally Posted by Rdurty2

All these complaints and no one takes their car to the dealer to have it looked at?

I took mine to the dealer. In fact I recently spoke with one of the techs that worked on it who mentioned the noise went away when they swapped out a shock from another vehicle. This led them to isolate the problem. He said there was quite a bit of back and forth with corporate about the issue. Unfortunately, I still have the same problem with the new shock - though it did improve for a time.

It's just speculation, but I think it has something to do with an internal component of the right rear shock related to the adaptive suspension. Though I'm not sure what is different with the right rear shock from the left rear.

I will say, however, that there is a black 1 1/2" pipe that is tucked into the right rear wheel well. I haven't traced it to see what it is or where it goes. If it was not properly secured, I could see it causing a similar sound- especially because it is only present in the right rear.

Weren't people in one the X3? forums complaining of a similar issue in the right front?

I'm living with mine for now- especially having already addressed it once and hearing that it is not unique to my car. I'm going to wait it out for a while until hopefully BMW figures out what it is.

[Rdurty2]

Originally Posted by kkgriss

I took mine to the dealer. In fact I recently spoke with one of the techs that worked on it who mentioned the noise went away when they swapped out a shock from another vehicle. This led them to isolate the problem. He said there was quite a bit of back and forth with corporate about the issue. Unfortunately, I still have the same problem with the new shock - though it did improve for a time.

It's just speculation, but I think it has something to do with an internal component of the right rear shock related to the adaptive suspension. Though I'm not sure what is different with the right rear shock from the left rear.

I will say, however, that there is a black 1 1/2" pipe that is tucked into the right rear wheel well. I haven't traced it to see what it is or where it goes. If it was not properly secured, I could see it causing a similar sound- especially because it is only present in the right rear.

Weren't people in one the X3? forums complaining of a similar issue in the right front?

I'm living with mine for now- especially having already addressed it once and hearing that it is not unique to my car. I'm going to wait it out for a while until hopefully BMW figures out what it is.

Good info, thanks. I will have my m240 in probably 2 weeks, hope it doesn’t make this noise, but if it does I can get it up and look around at things.

Frustrating to deal with crap like this on new cars, especially at this price point.

[MattM240eye]

A few of us have had it looked at, with no real answers. We have had them up on the lift with nothing of note. It just kinda sounds like something in the trunk while you are driving on bumpy roads. I had the opportunity to drive someone else's as well, and they had the same sound. I think it has something to do with the adaptive suspension, it doesn't effect the driving of the car at all, or the fact that it's an absolute riot to drive. Butt I'm sure we will learn more as time goes on.

[Rdurty2]

Anyone with the clunk without adaptive suspension?

Also does different suspension modes have any effect on it?

[emcee1011]

How loud is this clunk? I mean can you actually hear it over music or exhaust? Just want to try to find out how annoying it will be since I don't have the car yet.

Also, I'm sure if it's this widespread there will be a service bulletin in the future with a fix/replacement.

[Caerus]

Yes you can hear it over music and exhaust, but less so if music higher in volume. It is not a constant thing. It depends on the road surface and vehicle speed. Most of the time bearable, but some times it is bothersome. I suspect it is more noticeable in sport mode, mainly because the suspension is stiffer.

New observation I just found out. If you are in sport mode or activate sprint mode and want to have some aggressive fast shifts up to red line, the benign thump is now a loud bang. The bang only happens on the up shift only. Never heard such a noise in any other car during a shift. When I try it in comfort mode, I can't duplicate it. But that mode is less aggressive and very smooth.

I was waiting for further information to come out about this issue, but I will now talk to my dealership about this.

[socal_driver]

Experienced the noise this morning and remembered this thread. I have a 240 with a Dec '21 build and I have about 4400 miles on it. Drove on rough surface in the default comfort mode and could clearly hear it as I had the stereo pretty low. As others have stated will probably keep an eye out on this thread and won't take it to service until my oil change interval.

[BMWM.D.]

Originally Posted by Rdurty2

All these complaints and no one takes their car to the dealer to have it looked at?

As mentioned, I’ve been a BMW technician for almost 20 years. I decided to give up on it for now, as I don’t want to blindly replace parts in hopes that something will eliminate the noise. It’s definitely still there, though music does mask it in most cases.

I’ve also realized it’s definitely worse with the suspension in the Sport setting. I played with my Sport Individual settings so the only change was the suspension mode, and I hear the thump much less frequently with suspension in Comfort mode. All other settings remain the same. Makes me think it’s something to do with the rear shocks; what I don’t know.

As a side note, I was wrong about the shock part numbers: left and right rear ARE the same. I do believe the shock mounts are side specific, though. My money is on one of the shocks, mounts, or software controlling them. These cars are still very new and uncommon, so I haven’t had a chance to drive any more. The only other M240 I’ve had a chance to drive made the noise, so that’s when I gave up. At least for now. I can’t imagine this is something BMW engineering isn’t aware of.