When you pick up your car check the covers for broken small bolts, two passenger side and three driver side. Airpark Chrysler in Scottsdale AZ resealed the covers on my '06 last October and I just today found the head broken off one on the passenger side. Parts guy at Mercedes said the five bolts are one time use, replace with new at reassembly. Within 50 miles of their leak repair job, two oxygen sensors failed, probably because RTV not "sensor safe" was used.
Helpful tip- Put a little white grease on the 5 fasteners that hold the engine cover, it goes on and off much easier.

11/18/13, the breather cover with the broken bolt, head sheared off by the dealer knucklehead and left for me to discover, was removed and cleaned up for a reseal. After removing the remainder of the bolt, probing the hole indicated it was partially blocked with RTV, that's what caused the knucklehead to snap the bolt. Using a bottom tap 5 mm x.08, the RTV was removed.