How to fix timing chain problems in the 2012 Mercedes-Benz E350 (W212) with the M276 engine?

Identify Symptoms

• Unusual rattling or ticking noise from the engine.
• Check Engine Light (CEL) is illuminated on the dashboard.
• Poor engine performance or misfiring.
• Difficulty starting the engine or rough idling.

Preparation and Safety

• Ensure the vehicle is parked on a flat surface and the parking brake is engaged.
• Disconnect the negative terminal of the battery to prevent accidental electrical issues.
• Gather necessary tools: wrench set, socket set, camshaft locking tools, timing chain toolkit, and a repair manual specific to the M276 engine.
• Wear safety gloves and goggles at all times.

Accessing the Timing Chain

• Remove the engine cover by lifting it off the mounting points.
• Drain the engine oil and coolant to prevent spills during the process.
• Remove components obstructing access to the timing cover, including the serpentine belt, water pump, and accessory brackets.
• Take off the valve covers to gain better access to the camshafts and timing components.

Locking the Camshafts

• Rotate the crankshaft pulley to align the engine at Top Dead Center (TDC) for cylinder 1.
• Use camshaft locking tools to hold the camshafts in place, ensuring they do not move during the chain replacement.

Removing the Old Timing Chain

• Remove the timing chain tensioner to relieve tension on the chain.
• Mark the position of the camshaft and crankshaft sprockets for reference.
• Remove the timing chain guides if they are worn or damaged.
• Carefully slide the old timing chain off the sprockets and remove it from the engine.

Installing the New Timing Chain

• Compare the old and new timing chains to ensure they are identical.
• Install the new chain onto the crankshaft and camshaft sprockets, aligning it with the reference marks.
• Install new timing chain guides if necessary.
• Reinstall the timing chain tensioner and ensure it applies the correct tension to the chain.

Reassembly and Final Checks

• Remove the camshaft locking tools and rotate the crankshaft by hand to ensure the timing components move smoothly.
• Reinstall the valve covers, water pump, accessory brackets, and serpentine belt in their original positions.
• Refill the engine with fresh oil and coolant.
• Reconnect the negative terminal of the battery.

Testing the Engine

• Start the engine and listen for any unusual noises, ensuring the timing chain operates quietly.
• Use an OBD-II scanner to check for any error codes that may indicate timing issues.
• Test drive the vehicle to confirm the repair was successful and the engine runs smoothly.