The 2021 E350 W213 with the M264 2.0L turbo four is generally solid but shows catastrophic engine failure tendencies tied to oil starvation and balance shaft module issues, mostly under 60k miles. When they fail, it's spectacular and expensive—think complete engine replacement territory.
M264 Balance Shaft Module Failure Leading to Catastrophic Engine Damage
Occasional · high severityTypical onset: 30,000-60,000 mi
Symptoms: Sudden severe knocking or rattling from lower engine, Metal shavings in oil during routine changes, Oil pressure warning light, Complete loss of power / engine seizure in worst cases
Fix: Balance shaft module grenades and sends metal through the entire oiling system, scoring bearings and cylinder walls. Almost always requires complete engine replacement or rebuild with all bearings, pistons, rings, and thorough block inspection. 25-35 hours labor for engine replacement.
Estimated cost: $15,000-22,000
Transmission Oil Cooler Line Leaks
Common · medium severityTypical onset: 40,000-80,000 mi
Symptoms: Transmission fluid pooling under vehicle front, Burnt transmission fluid smell, Harsh shifting or slipping when fluid level drops, Low transmission fluid warning on dash
Fix: The quick-connect fittings on cooler lines corrode or the rubber sections crack. Replace affected lines and top off fluid. Some cases require full cooler replacement if internal failure. 2-4 hours labor depending on access.
Estimated cost: $600-1,400
Transmission Mount Collapse
Common · low severityTypical onset: 50,000-90,000 mi
Symptoms: Clunk when shifting from Park to Drive or Reverse, Excessive vibration at idle, Drivetrain slap on hard acceleration, Visible tearing or fluid leaking from mount
Fix: The hydraulic transmission mount deteriorates and loses its damping ability. Replacement is straightforward—support the trans, unbolt old mount, install new OE or aftermarket. 1.5-2.5 hours labor.
Estimated cost: $450-750
Fuel Filter Clogging (Early Production Units)
Occasional · medium severityTypical onset: 20,000-50,000 mi
Symptoms: Rough idle or hesitation under load, Check engine light with lean fuel trim codes, Hard starting after sitting, Loss of power on highway acceleration
Fix: Some early 2021s left the factory with contaminated fuel systems or poor-quality filters. Replace in-tank fuel filter and pump assembly if contaminated. Labor intensive due to tank drop. 3-5 hours labor.
Estimated cost: $800-1,600
Turbocharger Wastegate Rattle
Occasional · low severityTypical onset: 40,000-70,000 mi
Symptoms: Metallic rattle on cold start that disappears when warm, Rattle audible during light throttle acceleration around 1,500-2,500 RPM, No performance loss initially, May eventually throw underboost codes
Fix: Wastegate actuator arm develops play or the flapper valve wears. Can sometimes be addressed with actuator replacement alone, but often requires turbo R&R and rebuild or replacement. 6-8 hours labor for turbo replacement.
Estimated cost: $2,200-3,800
Coolant Thermostat Housing Leak
Occasional · medium severityTypical onset: 60,000-100,000 mi
Symptoms: Coolant weeping from front of engine, Sweet coolant smell in cabin or engine bay, Slow coolant loss over time, Overheating if neglected long enough
Fix: Plastic thermostat housing cracks at mounting points or seals fail. Replace entire housing assembly with updated part. Requires coolant drain and refill with proper MB coolant. 2-3 hours labor.
Estimated cost: $500-900
Great car when it works, but the M264 engine is a ticking time bomb—only buy with full MB service history and a comprehensive warranty, or be prepared to gamble on a $20k engine replacement.
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.