2005 — 2012
3.0L (OM642) - R280 CDI/R300 CDI/R320 CDI/R350 CDI V6 Diesel
Diesel
Observe the transmission shifting when cold; if you notice any shuddering or hesitation, it is worth investigating the conductor plate or torque converter health, as these are common areas for attention in higher-mileage W251 units.
Cycle through all suspension height settings; listen closely for any air compressor noise or uneven leveling, as the Airmatic struts and compressor bags may require servicing as they age.
Turn the steering wheel lock-to-lock while stationary; check for any whining sounds from the power steering pump or signs of leaking fluid around the rack, which are items to monitor on these V6 diesel models.
Open the bonnet while the engine is idling and look for any signs of oil seepage around the turbocharger intake seal, often referred to as the 'purple seal', which can drip onto the swirl motor linkage below.
Usually the time to evaluate the state of the timing chain and tensioners, ensuring the engine has had consistent oil changes to maintain longevity.
Consider having the air suspension bags and shock absorbers inspected for signs of fatigue, as these are essential for maintaining the R-Class ride quality.
Check the condition of the DPF (Diesel Particulate Filter) and exhaust sensors, as they may require professional cleaning or attention depending on the vehicle's driving history.
Stick to a strict engine oil and filter change interval every 10,000km to protect the OM642 turbocharger bearings.
Ensure the transmission fluid has been flushed; while Mercedes initially suggested 'sealed for life', a 60,000km interval is often considered best practice for the 7G-Tronic gearbox.
Keep the sunroof drains clear of debris to prevent water ingress into the cabin electronics, a simple task that saves a lot of trouble.
Monitor the coolant level regularly, as small leaks in the cooling system can lead to overheating if left unchecked.
Keep the cabin air filter fresh to ensure the climate control system remains efficient and the windscreen remains clear during wet NZ winters.
Estimated repair costs if issues arise
If the vehicle begins to sag overnight or the compressor struggles, you might eventually need to budget for replacement air struts or the pump module. It is a vital part of the comfort experience.
The OM642 engine utilizes a seal at the oil cooler that can perish over time. It is a labour-intensive job involving the removal of the intake manifold, so it is a good one to plan for if you notice oil residue in the 'V' of the engine.
Depending on the car's history, you might eventually need to budget for a repair to the transmission control module if gear shifts become erratic. It is common to consider this as part of long-term ownership of an automatic Mercedes of this era.
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Disclaimer: This report is generated with the assistance of AI analysis based on verified automotive data. While we strive for 100% accuracy, enthusiasts should always conduct physical inspections and consult service records. View Full Disclaimer