2010 — 2013
3.0L (OM642) - R300 CDI BlueEfficiency/R350 CDI 4MATIC Diesel
Diesel
Test drive task: Perform a full-lock turn at low speed in a car park. | Description: Listen for any rhythmic clicking or binding sounds from the front end, as the 4MATIC systems and front CV joints can experience wear after high mileage.
Check this by: Opening the hood while the engine is idling and looking at the valley of the engine. | Description: Inspect the area around the turbo and intake manifold for signs of oily residue, which may indicate the common oil cooler seal weep or intake swirl motor issues typical of the OM642 engine.
While driving: Observe the instrument cluster closely for any flickering or warning messages. | Description: The W251 is known for sensitive electronics; ensure that all infotainment functions and the air suspension settings cycle through their options without hesitation.
Check this by: Engaging the air suspension and adjusting the ride height through the settings menu. | Description: Ensure the vehicle rises and lowers evenly without triggering a 'Visit Workshop' error, as the air springs and compressor are parts that eventually reach the end of their service life.
Usually the time when transmission fluid and filter service is due if not already recorded.
Consider checking the condition of the turbo resonator and DPF (Diesel Particulate Filter) efficiency.
Common point where suspension components like control arms and air bags may warrant a thorough inspection.
Verify that the transmission fluid change was performed at the correct intervals as per Mercedes-Benz specifications.
Ensure all recall work, particularly regarding the brake booster if applicable to your specific NZ import, has been addressed.
Confirm that high-quality synthetic engine oil has been used, as the OM642 engine relies on this for turbo longevity.
Regularly clean the drain tubes near the windscreen to prevent water ingress into the cabin electronics.
Keep a close eye on battery health, as these cars are quite sensitive to voltage drops.
Estimated repair costs if issues arise
If the vehicle begins to sag overnight or the compressor struggles to lift the car, it is worth planning for a refresh of the air springs. Replacing these ensures the signature Mercedes comfort remains intact.
If you notice an oil leak appearing in the engine valley, this involves significant labour to reach the seal. It is a common maintenance item for the OM642 engine as it reaches higher age.
To keep the 7G-Tronic transmission shifting smoothly, a periodic fluid and filter change is vital. Budgeting for this will go a long way in protecting the longevity of your drivetrain.
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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