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2020 MERCEDES-BENZ GLE350D W167

2.9L I6 Diesel OM656•AWD•AUTOMATIC•diesel•turbo
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5-Year Cost of Ownership
$38,858 maintenance + known platform issues
~$7,772/yr · 650¢/mile equivalent · $7,213 maintenance + $28,725 expected platform issues
Common Problems & Known Issues

The 2020 GLE350d W167 with OM656 diesel has proven catastrophically unreliable due to a widespread engine defect causing catastrophic internal failures. Multiple class-action lawsuits exist for connecting rod bearing and piston failures requiring complete engine replacement, often under 100,000 miles.

OM656 Connecting Rod Bearing Failure (Class-Action Defect)

Common · high severity
Typical onset: 40,000-90,000 mi
Symptoms: Metallic knocking from engine bay, especially cold start, Check engine light with low oil pressure codes, Metal shavings in oil during changes, Sudden catastrophic engine failure with no warning
Fix: Complete engine replacement or full rebuild required. Rod bearings disintegrate, sending metal through entire lubrication system contaminating crank, block, and oil pump. 25-35 labor hours for engine R&R plus machine work. Many dealers replacing entire long blocks under goodwill or extended warranty.
Estimated cost: $18,000-28,000

Piston Ring Land Cracking and Piston Failure

Common · high severity
Typical onset: 50,000-100,000 mi
Symptoms: Excessive oil consumption (1 quart per 1,000 miles or worse), Blue smoke on acceleration, Loss of compression in one or more cylinders, Rough idle and misfires
Fix: Piston ring lands crack due to thermal stress and inadequate material specs. Requires complete engine disassembly, new pistons, rings, honing, and often crank polishing if contamination occurred. 30-40 hours labor if block is salvageable. Often discovered during bearing failure diagnosis.
Estimated cost: $15,000-22,000

Transmission Oil Cooler Leaks

Occasional · medium severity
Typical onset: 60,000-100,000 mi
Symptoms: Transmission fluid visible under vehicle, front-center area, Transmission running hotter than normal, Harsh shifting when cold, Low transmission fluid warning on dash
Fix: External cooler lines or internal radiator cooler seals leak. External lines are 2-3 hours, but internal cooler failure risks cross-contamination of coolant and ATF requiring full flush. Check both systems when diagnosing.
Estimated cost: $800-2,200

9G-TRONIC Transmission Mounts Collapsing

Occasional · low severity
Typical onset: 70,000-110,000 mi
Symptoms: Clunk when shifting from Park to Drive/Reverse, Vibration at idle in gear, Excessive drivetrain movement felt through chassis
Fix: Hydraulic transmission mounts fail, especially passenger side. 2-3 hours per mount. Verify both engine and trans mounts during inspection as they share load.
Estimated cost: $600-1,200

Fuel Filter Housing Leaks and Clogging

Occasional · medium severity
Symptoms: Hard starting or extended cranking, Fuel smell near engine bay, Loss of power under load, Diesel weeping from filter housing
Fix: OM656 uses plastic fuel filter housing that cracks or develops o-ring leaks. Filter clogs faster with US diesel quality. Replace every 20k miles regardless of spec. Housing replacement is 1.5-2 hours, but often done with filter service.
Estimated cost: $400-800

AdBlue (DEF) System Faults and Crystallization

Occasional · medium severity
Symptoms: AdBlue warning light with range countdown to no-start, Rough idle or limp mode, DEF system malfunction message, Crystallized deposits visible in filler neck
Fix: DEF injector, heater, or lines crystallize from poor-quality fluid or infrequent use. Tank and lines may need flushing, injector is 3-4 hours to replace. Prevention: use OEM DEF, drive regularly, never let tank run below 1/4.
Estimated cost: $1,200-2,800
Owner tips
  • Check service history for TSBs and warranty extensions on OM656 engine — Mercedes has issued multiple campaigns but not full recall
  • Oil analysis every 5,000 miles is mandatory for early bearing failure detection; watch for iron and aluminum spikes
  • Budget $2,000/year minimum for maintenance beyond the catastrophic engine risk — these are $70k+ vehicles with premium part prices
  • Extended warranty is essential if purchasing used; ensure it covers internal engine components explicitly
Absolutely do not buy without comprehensive warranty covering engine internals — the OM656 defect makes this a financial time bomb despite the otherwise excellent W167 platform.
AI-assisted summary drawn from NHTSA recall data, our labor-times database, and platform knowledge. Not a substitute for a pre-purchase inspection on a specific vehicle.
525 jobs across 17 categories
🔧 Database maintained under the daily editorial review of Chris Hackleman · Master Technician · 20+ years and Jeff Moore · Master Lexus & Toyota Mechanic · 20+ years.
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