I have a lot of interior sounds as well. It's been a painful and slow process eliminating one sound at a time. I was able to eliminate quite a few already. So far here's what I got.
1. Creaking sound coming from the instrument cluster
- I traced this to the plastic housing of the instrument cluster. The housing is essentially two pieces of plastic held together by a screw. This screw also is what secures the instrument cluster to the dashboard of the car. Due to a design flaw, in time, this screw that holds the cluster in place will loosen up and cause the two plastic housing parts to rub against each other causing the creaking sound. I removed the cluster, pulled apart the two housing pieces and literally super glued them together. The sound went away and never came back!
2. Creaking/ticking sound coming from the instrument cluster exterior plastic trim
- this one really got me for a while since I couldn't tell if the sound was coming from the instrument cluster itself or from the plastic exterior trim that covers the corners of the instrument cluster. I only was able to finally figure out this was also a culprit of noises once I super glued the instrument cluster. Since the instrument cluster wasn't making any noises anymore, it was obvious that the noise was coming from the plastic cover trim. I then proceeded to strategically place felt on key places of the trim. I also placed felt on the inner portion of the dashboard where plastic trim and dashboard meet. I couldn't take a picture of it anymore since it was at such an odd angle but here are pictures of the felt on the trim.
I later found out that on the 2008 and up models of the C class, the trim already has felt placed by the factory. But I still seemed to have needed more felt for my car in order to stop the noise completely.
I then reinstalled the trim and the sound went away.
3. Ticking sound coming from the center console
- I literally took everything in the center console out of the dashboard and by process of elimination, I was able to pinpoint the sound coming from behind the COMMAND screen.
I then proceeded to yank out the COMMAND screen and low and behold, behind it, I found a cable that moves up against it's plastic housing. I played around with it, moved it around and true enough, it made the exact same sound that I've been hearing.
I also was able to take pictures of this DIY so here's a shot of the cable that I'm talking about behind the COMMAND screen. I pulled it out of its housing but when reinstalled back in the the dash, the cable is supposed to be flush inside the housing.
I then proceeded to wrap the cable with felt tape (sorry I don't have a picture for this, was too excited to have discovered the source of the rattle) and put everything back together. I then took the car out for a spin and true enough, I couldn't hear the ticking anymore and I still don't hear it anymore.
Just for kicks, here's a shot of everything in the center dash removed.
There is also a creaking/ticking sound coming from the plastic housing of the COMMAND screen itself. Like the instrument cluster, the housing for the COMMAND screen is held together by two half pieces of plastic. This eventually will rub against each other when driving over rough roads and will start to make noises in time. I didn't bother fixing this anymore as it required for me to literally pull apart the screen's housing and most likely I'd have to super glue them together to prevent them from rubbing against each other. I'm afraid I might damage the screen and opted not to do it anymore. Plus the sound seems to go away when the screen is in the closed position.
4. Ticking sound coming from the A-pillar
- stuffed foam inside the cover and sound went away.
5. Rattle coming from the center console where the gear shift is
- I removed the trim surrounding the gear shifter and took the car for a spin. The sound was gone so I was able to narrow it down to the trim causing the sound. When I took a closer look at the trim, I notice that it's held in place inside the center console by friction by clips. The clips have come loose and were moving around. When you shake the trim on its own, you will hear the clips rattle around. I figured this might be causing the trim to loosen up when driving so I super glued the clips and for good measure, I placed felt all around the corners of the trim, to make sure it's a real snug fit when placed back in the center console. Reinstalled the trim and the sound went away. Sorry, I don't have any pictures for this one.
6. Ratting coming from interior trim surrounding the AC controls
- this one was fairly simple. I removed the trim and placed felt all around the corners of the trim. Made the fitment real snug and the sound went away as well.
7. Rattle coming from interior trim on door
- for this I removed the door trim, took out the side panel and inserted felt between the trim and door panel. I re-tightened up the screws holding the trim together and the sound went away. There is a inherent design flaw here where the screws Mercedes used to hold the trim in place doesn't secure it properly. Here's a shot of the screws.
I'm not to sure what kind of screws those are but they really don't work! They don't tighten at all. My theory is that they're designed to break off in an event of a side impact so the interior trim breaks off as once piece and doesn't splinter and kill you?
Here's a shot of the door panel with the felt placed in order to give the trim a snug fit.
I also put felt on the trim itself to make sure it stays.
8. Rattle coming from center speaker
- I removed the center speaker and placed felt to push up against the speaker. Sound went away. Here's a picture of the felt in place.
9. Creaking sound coming from the black plastic trim on door, between the window and rubber seal for the door
- this was solved by removing the black plastic trim and laying felt all over the inner portion of the plastic trim. Reinstalled the trim, looked a little puffy, but the sound went away. Sorry, I don't have pictures of this one either but I only did one door for my car and I will take pictures when I do the other three doors.
Now on to sounds I currently hear and I'm still working on trying to find out where they're coming from.
1. A series of ticking sounds coming from the rear interior of the car
- Most likely from the rear ceiling or umbrella shelf. Seems to just happen randomly, when stopped or when moving. Happens intermittently so its hard to determine where its coming from.
2. Ticking sound coming from the rear view mirror area
- Mostly happens when on rough roads. I believe it's coming from the base of the housing of the rear view mirror.
3. Creaking sound coming from the passenger front seat
- I've read online that this could be a loose screw underneath the seat. I have yet to look into this and will do so the next time I get the chance work on my car.
4. Rattle coming from the left and right front speaker cover on the dashboard -
This is the long thin cover on both corners of my dashboard.
5. Ticking sound coming from the sun roof
- not sure about this one. I'm scared to touch the sun roof though so I'll just leave this one to the dealers. Though I'm quite certain it's a long shot that they might be able to fix it.
Hope this helps! If you have any possible solutions for the sounds I still have and where they're coming from, please let me know. Would appreciate any help. Thanks!