The OM646 is notorious for the crankshaft bolt loosening. A generic manual says: "Torque to 200 Nm."
In 2006, the engine was updated to the "EVO" name, which offered improved performance, reduced compression ratios, and better cold starts. 2. Technical Specifications & Features Mercedes Workshop Manual Om646 Engine
Without this, you will break the plastic intake manifold rails. The OM646 is notorious for the crankshaft bolt loosening