Knocking sound from roof?
 

Hi everyone so I have 2011 c300 with 2500 miles on it now. And recently I have begun to hear a knock sound common from the roof of the car whenever I drive on a speed bump or up or down a driveway. It only happens sometimes and I don't know know why it is doing this. It happens with the sunroof shade open and closed. Does anyone else have this issue or am I just being anal? I'm not sure what it is and can't figure out where it is coming from. Thanks

Not sure if it is the same thing but I had this issue with my CTS and the dealer had to adjust the tension on my sunroof - it was actually was popping open about a 1/4 inch and slamming back closed when going over a quick bump as you describe.

Do a quick check and see if you can push up (lightly) on the sunroof when it is n the closed position.

Is it a knocking or a rattle? I used to have the rear dome light rattle under situations you describe. Brought it in and they fixed it. I believe they took it down and applied some felt.

check for loose stones as well.

Thanks guys. But I checked the sunroof and it moves up just a bit but it's nothing I can find that rattles. It may be the rear dome light. Today when I was driving it actually doesn't sound like a knock but more of a rattle but only does it once. It's a single click then it stops. It's nothing that continues to rattle but does it at least a few times when driving.....

I know that seems confusing but not sure how to explain it.?.?. Lol

I have the exact same problem on my car. I haven't been able to solve it yet and the dealer said the only way for them to check is it remove my ceiling. Something I wasn't willing to do just yet. They did find creaking sounds and popping sounds coming from my B pillar. They put foam in between where the ceiling meets the B pillar. It seemed to have helped. I also used get a lot of popping sounds coming from the black plastic cover between the door in the seal. Again, they put foam and some fillers and the sound only comes out when I drive over a steep driveway at an angle.

Thanks, it is a popping/ knocking sound as well whenever I go down my driveway or on a speed bump. Seems to happen whenever the car is angled. It's very odd but not sure where it us coming from so I am going to take to the dealer soon to get it fixed. I mean it is new car so I'm going to get it fixed asap.

I have the Same problem with my 2011 C300! I have taken it back to the dealer 3 times for service, and they still have not been able to identify the problem!