Picked up a 2010 C350 4M this week and...
Luckily it stayed relatively intact as one piece of glass so I taped it up with several layers to keep it as one piece and to try and keep it waterproof. I also taped the underside so there wouldn't be any shards falling on my head or the sunscreen.
I called the dealership and they won't be able to get a new piece of glass for 10 days because it's coming from Germany...so hopefully my DIY waterproofing holds up...
I don't know if it happened because of a rock hitting it...or some flaw in the glass and I guess I'll never know for sure.
Other than that this car is amazing! I had a 2005 C230 Sport and the upgrade has been well worth it all around so far.



