Mercedes Benz notes that unnecessary resealing is being performed on cylinder heads when the cylinder head is not the root cause of an oil leak.
A video has been created which outlines the proper procedure to help identify the source of engine oil leaks. The video is available as of the 11-20-11 Star Diagnosis release and can be accessed through the following path: SDmedia>Symptoms/Topics>Engine>AR – Localize oil leaks on major assemblies [Model Passenger Cars].
The new generation of Mercedes-Benz engines (M272 amd M273 engines) feature chemical sealers (formed in place gaskets) applied to sealing surfaces by robots during the engine assembly process. This engine sealing technique (RTV) uses the silicone rubber compound. This precise and uniform application of silicone at the factory insures a proper adhesion and a leak-tight connection that rarely leaks.
During necessary engine resealing repairs, care must be taken in preparing surfaces and applying silicone compound. Do not clean surfaces with any abrasive materials or sharp tools. Only approved Loctite cleaning spray must be used when prepping engine surfaces. Only 1mm-thick silicone bead should be applied uniformly to one side of sealing surfaces in a precise pattern. A small amount of oil should be applied to camshaft bearings. Sealing surfaces must be assembled within 10 minutes of sealant application.