Mercedes has made a DTB (diagnostic trouble bulletin) to notify owners of a problem with their PCV valve. DTB S-B-01.20/24 FEB09 ML63, C63, CLK63, E63, CL63, CLS63, S63, SL63, and R63 up to engine # ...

First, remove the plastic engine cover to reveal the rocker cover and the PCV valve. With the engine running, place a small piece of paper over the hole in the PCV valve. If the paper is drawn to the ...