Mercedes-Benz C-Class: M272 V6 Balance Shaft Sprocket Premature Wear

The M272 3.0 and 3.5-litre V6 engine uses a balance shaft driven by a sprocket with an undersized tooth profile on early production units. The sprocket teeth, made from a sintered metal compound, wear at an accelerated rate, causing the balance shaft drive chain to jump or the sprocket to strip entirely. When the balance shaft timing is lost, the engine produces severe vibration but continues to run. However, the drive chain that also powers the oil pump runs from the same system in some configurations, meaning complete oil pressure loss and catastrophic bearing failure is possible. Mercedes acknowledged this defect and changed the sprocket specification, but a significant number of pre-2008 build-date M272 engines contain the worn sprocket design. The repair requires engine removal or at minimum full front-end strip to access the timing case.

• Progressive increase in engine vibration at idle and through the rev range
• Rough running or shaking felt through the steering wheel and seat at idle
• Check Engine light with camshaft or crankshaft correlation fault codes
• Metallic debris found in engine oil at service (indicates sprocket tooth material)
• Engine rattle from timing area that worsens with engine age and mileage

1. 1

   Request full service history to determine build date and mileage.

2. 2

   Engines built before approximately late 2008 and with high mileage (over 120,000 km) are at highest risk.

3. 3

   Start the engine cold and warm and feel for vibration through the car — balance shaft faults produce a characteristic whole-body shake.

4. 4

   Retrieve fault codes for any camshaft or balance shaft correlation errors.

5. 5

   Ask specifically whether the balance shaft sprocket has been replaced with the updated specification part.

$2,200 to $5,500 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 balance shaft sprocket been replaced with the updated Mercedes specification part?”
• “What is the engine build date (visible on the engine data plate)?”
• “Has the car ever produced unusual vibration or shown timing-related fault codes?”
• “Has engine oil ever shown metallic particles or a grey sheen at service?”

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.