Just purchased a C230 sedan. This morning I noticed that the rear wheel wells don't have a plastic membrane, rather they have a lining that is similar to what is in the trunk. This seems very strange. I went over to the Mercedes dealership and checked out some other C-Class models, and they had the same thing. What is the deal here? Why would they use this type of lining for the rear wheel wells?

Also, when I was at a stop light today I heard a very fast vibration noise coming from the rear of the car. It wasn't a loud vibration, but it was very fast(many times a second). When I got out of the car(car was turned off) I heard the noise again. It sounded like it was around the muffler area. Any ideas here?

I am not sure about the noise. But the rear wheel wells have the "fabric" lining to reduce noise. It works great. I rode in a car that had the fabric lining taken out and the noise increase was substantial.

Rapid ticking or clicking from the exhaust is normal and seems more pronounced when the car is new. It's related to thermal expansion (and contraction after shut-down) of the exhaust system's components.

The pupose of the carpet like material in the rear wheel wells is to reduce spray on wet roads. Noise reduction, if any, is a secondary benefit.

my rear wheel wells are lined with plastic just like the fronts.

That's because it doesn't rain much in the Phillipines.

1st time at the dealer they couldn't "reproduce" it. I am taking it in again and this time I am going for a ride with a tech in the car to demostrate the noise. It only happens on hot days when I push the car a bit and then stop at a light. It must be some temperature related thing like expansion/contraction of something. Can barely hear it from outside the car but from inside it sounds like a 'thump-thump' noise.


CZ

CZ, let me know what you find out. I'm assuming yours is a rapid "thump-thump" sound(many times a second). When it happens it's not loud, but it is noticeable. Like I said, when I got out of the car I could hear it as well. It sounded like it was coming from underneath the car, just behind the rear wheels.

When I was driving today I didn't hear anything, but then again I also had the music up and really wasn't "trying" to find the problem. Tomorrow I will take it out and see if I can "reproduce" it.