Mercedes is aware of this problem, and yes I have seen it before. They even came up with a gasket that has a pan in it to keep the parts of the vacuum pump from entering the timing chain/ oil drive area of the engine. The new engine will have this gasket in it and the updated timing chain and sprocket on the cam and will be reliable. I'm sorry this happened to you but I stand behind the Mercedes as a very safe, reliable car!
ASE CERTIFIED MASTER AUTO TECHNICIAN
LEAD TECHNICIAN FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM