The 2007 E320 CDI with OM642 V6 diesel is known for solid fuel economy and torque, but suffers from catastrophic engine failures due to defective balance shaft gears and swirl flap issues, plus typical Mercedes transmission cooling and mount problems that plague the W211 platform.
Balance Shaft Gear Failure (OM642 Catastrophic Engine Damage)
Common · high severityTypical onset: 80,000-150,000 mi
Symptoms: Metallic rattling from engine at startup or idle, Check engine light with timing correlation codes, Sudden catastrophic failure: metal shavings in oil, total seizure
Fix: Balance shaft gear strips teeth, dumps metal into oil system, destroys bearings/crank/pistons. Requires complete engine rebuild or replacement. 25-35 labor hours for short block swap, 40+ for full rebuild with crank/bearings/pistons. Many shops recommend used/reman engine due to cost.
Estimated cost: $8,000-15,000
Intake Manifold Swirl Flap Failure
Common · high severityTypical onset: 60,000-120,000 mi
Symptoms: Loss of power, rough running, Check Engine Light, Rattling noise from intake manifold, Metal flap arms break off and get sucked into cylinders causing piston/valve damage
Fix: Swirl flap linkages break, flaps fall into intake runners and can be ingested by engine. Many owners preemptively delete or replace manifold. Delete kits available. If ingested, requires head removal and cylinder inspection. 6-8 hours for manifold replacement, 15+ if engine damage occurred.
Estimated cost: $1,200-2,500 (preventive), $5,000+ (if engine damage)
Transmission Oil Cooler Leak/Failure (722.6 Five-Speed)
Common · medium severityTypical onset: 70,000-130,000 mi
Symptoms: Transmission fluid leaking from cooler lines or radiator area, Harsh shifting or slipping when fluid gets low, Pink fluid mixing with coolant if internal cooler fails
Fix: External oil cooler lines crack or cooler itself leaks. If cooler inside radiator fails, you get cross-contamination requiring full trans flush and possible valve body damage. Replace cooler and lines preventively. 3-5 hours for external cooler, 6-8 if radiator replacement needed.
Estimated cost: $800-1,800
Transmission Mount Collapse
Common · low severityTypical onset: 80,000-150,000 mi
Symptoms: Clunk or thud when shifting from Park to Drive/Reverse, Vibration at idle in gear, Visible sagging of transmission when inspected on lift
Fix: Hydraulic transmission mount fails, allows excessive drivetrain movement. Common W211 issue. Straightforward replacement. 1.5-2.5 hours.
Estimated cost: $400-700
Diesel Injector Failure and Carbon Buildup
Occasional · medium severityTypical onset: 100,000-180,000 mi
Symptoms: Rough idle, misfires, black smoke, Hard starting when cold, Poor fuel economy, loss of power
Fix: Piezo injectors fail or get carboned up. All six should be tested/replaced together. Also requires walnut blasting intake valves (direct injection carbon). 8-12 hours for injector set plus intake cleaning.
Estimated cost: $3,000-5,500
Fuel Filter Housing Leak
Occasional · low severityTypical onset: 80,000-140,000 mi
Symptoms: Diesel fuel smell in engine bay, Visible leak at filter housing or primer pump, Hard starting or loss of prime
Fix: Plastic filter housing cracks or o-rings fail. Replace entire housing assembly with upgraded metal unit if available. 1.5-2 hours.
Estimated cost: $300-600
Airmatic Suspension Failure (if equipped)
Common · medium severityTypical onset: 70,000-120,000 mi
Symptoms: Airmatic warning, vehicle sags at one or more corners, Compressor runs constantly, Harsh ride or nose-dive when braking
Fix: Air struts leak, compressor wears out, valve block fails. Expensive repair; many convert to coil springs. Individual strut: 2-3 hours. Compressor: 3-4 hours. Coil conversion: 4-6 hours.
Estimated cost: $1,500-3,000 per corner (air), $2,000-3,500 (full coil conversion)
Only buy if you can afford a $10k+ engine replacement or find one with documented balance shaft gear update; otherwise the OM642 is a ticking time bomb that makes this a hard pass for most buyers.
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.