Mercedes — Workshop Manual Om646 Engine [updated]

If you are using a workshop manual for routine DIY maintenance, you will frequently refer to these sections:

Without a manual: You remove the valve cover, see slack in the chain, and try to replace it. You don’t lock the camshafts, the crank moves, and when you start the engine, the pistons hit the valves. Mercedes Workshop Manual Om646 Engine

| Fastener | Replacement mandatory? | Notes | |----------|------------------------|-------| | Cylinder head bolts | Yes | Plastic deformation | | Connecting rod bolts | Yes | Stretch bolts | | Main bearing bolts | Yes | Do not reuse | | Crankshaft pulley bolt | Yes | Failure causes engine destruction | | Injector hold-down bolt | Yes | Over-torque cracks injector | | Flywheel bolts | Yes | Auto-transmission applications | If you are using a workshop manual for

The Workshop Manual (often accessed via Mercedes' WIS - Workshop Information System) is typically divided into key groups. For the OM646, the following sections are most frequently referenced: see slack in the chain

Injector & common-rail service

offer versions that are user-friendly for home mechanics, though some reviewers note that technical sections like "electrics" can be less detailed than official factory literature. Critical Technical Specifications Standard OM646 OM646 EVO (Post-2006) Power Output 65–110 kW (88–150 hp) Up to 125 kW (170 hp) 220–330 Nm Up to 400 Nm Compression Ratio Glow Plugs User Perspective & Feedback

In 2006, the engine was updated (OM646 EVO) with a new turbocharger and ceramic glow plugs for better cold starts. 2. Common Maintenance: What Your Manual Will Highlight