FINALLY I WON! The noise comes from front shock absorber. It may caused by the failure of Bilstein DampTronic module. If you unplug the cable which linked to the module, NO NOISE ANY MORE!
I checked with Bilstein reseller for the replacement, and it won't be cost much. Of course, you can enjoy it free by disable the function.
I love my car again...

 

Thank you so much for trying to find the issue!!! By any chance you can post the part number for the module? Since it isn't a major problem and now I know what is the issue, I will not be in a rush to get it replaced.

 

You have to get a new shock.

 

Will the car throw any error codes if you just unplug the module? Did you just unplug module from 1 side or both of the fronts? The module is what allows us to control the suspension stiffness on the center console above the traction control button correct?

 

No way! Congratulations man I'm so glad you found that issue. Seriously well done on your perseverance and even buying a special microphone haha. You are a hero to others who will have this issue in the future 🏆

Lucky you didn't buy a new steering rack, too.

 

No error from the dash but probably can find it by using diagnosis tool. One more thing you need to note. Please set suspension stiffness mode in advance if you decide to remove the noise by unplugging cable. Because once you unplug the cable, the mode will be locked unless you put the cable back.

Here is the OE part information may help you.

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You are my hero too! Always remind me that don't buy new parts before find the issue out! Thank you buddy!

 

I have the same noise and have had it since the car was new - see you tube video ‘Mercedes W205 C63 Rear End Whine’. It appears to be coming from the offside rear (RHD Car). Both rear shock absorbers were replaced under warranty after 18 months as they were leaking. Would I have Bilstein Damptronic Modules on the rear and should they have been replaced/tested at the same time?

Many thanks, Jonathan

 

Well the video in the thread you mentioned isn't the sound OP and I are experiencing exactly. The sound we hear is like a telegraph/sonar sound that is audible in parking lots or uneven surfaces going under about 10 mph. Once driving beyond parking lot speeds, the sound is too faint to possibly hear. To answer your question, each strut front and rear has the damptronic module and they are actually one piece. So if you had your struts replaced then the module has been replaced as well.

 

I do have somewhat of a similar noise, but it's more consistent, not sounding like sonar, more like a high pitch background noise. vidmate appsave insta

 

If there is a problem with the Damptronic module is this not flagged by Mercedes diagnostic or Is the submarine sound the only indication that the module 8s not working?

 

I am not entirely sure about it being flagged by Mercedes diagnostic, but, I don't think the sounds means the module isn't working. I have the sound which is pretty noticeable when in parking lots with no music on, but my suspension adjustability still works fine.

 

Do you know if Bilstein are aware of this issue and whether they consider it a fault?

Many thanks

 

My suspension is working but with the sound. I believe this is a common issue, because many people have same feedback. But i guess not everyone is so sensitive like us about the noise. And so far i have no plan to replace the suspension and it won't bother me, just because i already know that.

 

Greetings from sweden,

I just posted a thread exatcly about the same noise but mine comes clearly from rear end. I assume and hope haha but must hearable from behind driver seat and but back seats it sounds all around but its very itchy and thin sound reapeatably.

as someone told before here: ”It's very subtle and seems to happen more when going slow over speed bumps or dips in the road. The car drives fine and its such a soft sound, I hadn't tried to track down what is causing it yet.

(I have gone through suspension without success, about to buy new bushings for rear diff, I really need to start somewhere…

Exactly ONLY on low speeds and bumpy road…

ill try to link the video otherwise visit my thread. I linked it in the comments.


*EDIT*

Holy sh*t thanks alot, it removed the contact from the damper I thought it was, JACKPOT right away the sound way gone!!! new damper inc, thanks alot for this forum and thread ill update mine and redirect to this one.

 

Sorry to hear about the issue, glad to hear you found the cause. The video you posted should also be helpful to others that are trying to identify the noise.

 

Wanted to update this thread as it was very helpful to finally get this issue taken care of with my coupe. It turned out that both my rear shocks were making this buzzing noise. It took three visits, a test drive with the foreman and involving the service manager to get this issue taken seriously. A bit frustrating that it took this much effort, but glad it finally is resolved. I still have to do some more driving and verify that the noise is a 100% gone. It is hot today, so my AC was blowing, but going up my driveway and into my garage I didn't hear the noise where I used to hear it. Now I also get the distinct impression that the suspension handles bumps better than before. The car felt more compliant over bumps that before could result in a somewhat sharp bang in the suspension. Have to do some more driving at different temperatures and on different roads to come to a final conclusion, but I'm inclined to say that the shocks are actually faulty if they make this noise. It's not that it rode bad before, but replacing the rear shocks seemed to have removed some rough edges.

The car seems to drive better overall in normal driving as they also updated the ECU due to a misfire I had during hard acceleration and the oil sensor telling me again to top off the oil, even though the dipstick says it's at max. More to come after I had some more driving time, but just in case anybody else is struggling with getting this resolved, below are the notes from the tech and how they troubleshooted it. Pretty much like OP did, by unplugging the shocks after I pointed them to the likely cause with the help of this thread, especially OP's video. If you are in the SF Bay Area, go see Dave, the foreman at MB of Walnut Creek. He now knows all about this issue.

 

Quick follow up. Had some more time to check it out on a cooler day w/o the AC blasting, and the noise is a 100% gone. Adjusted the tire pressure since it was a bit low after 2.5 weeks and went on an errand, so drove the typical roads I drive around here, some smooth, some a bit broken up, speed bumps etc, and it most definitely has an improved ride at low speeds compared to before. I'll have to take it to the canyons to see if it changed anything for high speed cornering, but at least on the highway so far it drives the same. It's gonna have to wait a few weeks, though. Just had hernia surgery two weeks ago, so need to wait before subjecting my body to g forces.