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Mercedes OM642
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Mercedes OM642
Verdict
RISKY · 48/100
Est. cost /3yr
€4,500-15,000 over 3 years depending on maintenance history and mileage, higher if oil cooler seals or timing chain require attention
Oil interval
10,000 km
Recalls
1
Worst issue
Timing Chain & Tensioner Wear
CRITICAL
Mercedes OM642
W164 · W164
Timing Chain & Tensioner Wear
€1,500-4,000
CRITICAL
Oil Cooler Seal Failure
€800-2,500
HIGH
EGR Valve & Swirl Flap Issues
€400-1,200
HIGH
Turbocharger & Actuator Fragility
€1,200-3,500
HIGH
Valve Cover Gasket & Ancillary Oil Leaks
€300-900
MODERATE
Mercedes OM642
W164 · W164
•Perform a cold-start and listen for any timing chain rattle lasting more than 2 seconds before buying
•Check the coolant reservoir for oily contamination and the oil filler cap for white emulsion indicating oil cooler seal failure
•Request full documented service history, verify oil was changed every 10,000 km or less with correct MB 229.51/229.52 spec oil
•Connect an OBD scanner and check for fault codes related to EGR, swirl flaps, turbo boost, and cam timing deviation
•Inspect the engine bay for oil staining around valve covers, oil cooler area, and turbo bracket mounting points
•Test drive under full load above 2,000 RPM to confirm no power choke or limp mode triggered by turbo or swirl flap faults
•Check for confirmation of the fuel injector line recall having been carried out, ask for dealer paperwork
Mercedes OM642
W164 · W164
Timing Chain & Tensioner Kit
Inspect tensioner notch position, replace full kit if 3+ notches visible or rattle present
120,000 km
Oil Cooler Seals
Inspect for cross-contamination at every service, plan replacement as preventive maintenance
100,000 km
EGR Valve
Clean or replace, inspect intake manifold for carbon buildup
100,000 km
Turbo Actuator
Test actuator function and scan for boost-related fault codes
150,000 km
Mercedes OM642
W164 · W164
Fuel Injector Line Cracking
On certain 2007-2012 model year OM642-equipped Mercedes-Benz SUVs (ML, GL, R-Class), a fuel injector line can crack over time and leak diesel fuel in the engine compartment, creating a fire risk.
Mercedes OM642
W164 · W164
✓Strong torque output (up to 620 Nm) makes it capable and effortless for an SUV
✓Aluminium block and heads keep weight competitive for a V6 diesel
✓When properly maintained with short oil intervals, the engine can achieve high mileage
✓Chain longevity is reported to be good with diligent oil changes, failures are strongly maintenance-related
✓Wide parts availability across multiple platforms reduces sourcing difficulty
Mercedes OM642
W164 · W164
Real consumption
10.6 L/100km
Official consumption
12.3 L/100km
Oil interval
10,000 km
Oil spec
MB 229.51 or 229.52 5W-30 fully synthetic diesel engine oil
Est. cost /3yr
€4,500-15,000 over 3 years depending on maintenance history and mileage, higher if oil cooler seals or timing chain require attention
Mercedes OM642
W164 · W164
190 hp · 440 Nm
2005-2009
224 hp · 510 Nm
2005-2009
258 hp · 540 Nm
2009-2011
261 hp · 620 Nm
2009-2011
The power output differences across ML280/320/350 CDI variants come from ECU tuning and turbo boost calibration, not a fundamentally different engine, so hp figure alone should not drive your buying decision. All variants share the same timing chain, oil cooler, EGR, and turbo actuator weak points. Focus on documented oil change history and cold-start chain rattle regardless of which power output you are looking at, and treat the BlueTEC facelift versions (2009 onward) as having marginally more mature emissions hardware, not a more reliable core engine.