Mercedes-Benz C-Class: M274 2.0T Timing Chain Tensioner Cold Start Rattle

The hydraulic timing chain tensioner on the M274 2.0 turbocharged engine loses oil pressure when the vehicle sits for several hours. On cold start, this produces a characteristic metallic rattle from the timing cover that typically lasts 2-8 seconds until oil pressure is restored and the tensioner re-extends. Repeated cold-start events accelerate chain guide and chain wear. If neglected, the timing chain can jump a tooth or fail catastrophically, causing severe engine damage requiring full replacement. This fault is closely related to the tensioner design shared across the M271 and M276 V6 families and was acknowledged by Mercedes-Benz through multiple technical service bulletins.

• Metallic rattling or ticking from the front of the engine on cold start lasting 2-8 seconds
• Rattle disappears once oil pressure is fully established
• Check Engine light with stored fault codes P0016 or P0017 (camshaft-crankshaft correlation)
• Rough idle or hesitation immediately after cold start
• In advanced cases, persistent rattle even after warm-up

1. 1

   Start the engine cold first thing in the morning and listen carefully at the front of the engine block for a brief metallic rattle lasting more than 2 seconds.

2. 2

   Scan for stored or pending fault codes related to timing correlation or camshaft position.

3. 3

   Review service history for consistent oil changes at or below 10,000 km intervals using MB-approved 229.5 or 229.51 specification oil.

4. 4

   Ask the seller to cold-start the vehicle without prior warming.

Parts involved: Timing chain.

$1,900 to $5,200 at New Zealand independent workshop rates. That is for this job on its own, not for the car.

An estimate, in NZD, for the repair as normally carried out. What a specific car costs depends on which part has failed and what it damaged on the way — treat this as the floor for a negotiation, not a quote.

• “Has the timing chain tensioner or timing chain been replaced or inspected?”
• “Has the vehicle always been serviced with MB-approved 229.5 spec oil?”
• “Have you ever heard a cold-start rattle from the engine?”
• “Are there any stored fault codes related to timing or camshaft position?”

The failure described above is documented in published sources — owner forums, technical service bulletins, recall notices and workshop write-ups — held in our fault database. The inspection instructions and the cost estimate are KickTyres’ own interpretation of them, and it is a starting point for an inspection rather than a manufacturer statement.