The W220 S320 CDI with OM613 engine is a comfortable cruiser plagued by catastrophic engine failures due to a factory piston-ring defect, combined with typical late-W220 air suspension and electronics gremlins. Many units have already failed or been rebuilt; surviving examples past 150k may be okay, but the engine is a ticking time bomb until proven otherwise.
OM613 Catastrophic Piston Ring / Bore Wear Failure
Common · high severityTypical onset: 80,000-140,000 mi
Symptoms: Excessive oil consumption (1 qt per 500-1000 miles), Blue smoke on startup and acceleration, Loss of compression, rough idle, misfires, Metal contamination in oil, eventual rod knock or seizure
Fix: Factory piston rings were underspecced — they wear grooves into the bores. Requires complete engine rebuild with oversize pistons, honing/sleeving cylinders, new rings, bearings, seals. 40-60 hours labor depending on shop access and whether block needs machine work. Many owners opt for used/reman engine swap instead.
Estimated cost: $8,000-15,000
Airmatic Suspension Strut Failure
Common · medium severityTypical onset: 100,000-150,000 mi
Symptoms: Vehicle sagging on one or both corners overnight, Airmatic warning light, 'STOP vehicle too low' message, Compressor runs excessively, pump failures follow, Visible oil/air leaks at strut bellows
Fix: Air struts leak at bellows or internal seals. Replacement with OE or Arnott aftermarket struts, 2-3 hours per corner. If compressor has been overworked, add another $800-1200 and 2 hours for pump replacement. Many convert to coil springs ($1500-2000 kit plus 6-8 hours labor).
Estimated cost: $1,200-2,500
Transmission Conductor Plate / Valve Body Electronics Failure (722.6 5-speed)
Occasional · high severityTypical onset: 120,000-180,000 mi
Symptoms: Harsh or delayed shifts, limp mode, No 5th gear, stuck in 2nd or 3rd, Transmission fault codes (input/output speed sensor, solenoid errors), Intermittent shifting issues when transmission is hot
Fix: 722.6 conductor plate (13-pin connector) cracks solder joints or corrodes. Requires transmission pan drop, valve body removal, replacement of conductor plate and often external wiring harness. 6-8 hours labor. Use OE or reputable reman (not cheap eBay units). Fluid and filter service mandatory during repair.
Estimated cost: $1,800-3,200
Transmission Oil Cooler Line / Radiator Failure ('Pink Milkshake')
Occasional · high severityTypical onset: 100,000-160,000 mi
Symptoms: Transmission fluid in coolant (pink/red milkshake in expansion tank), Coolant in transmission (burnt ATF, erratic shifts), Overheating transmission or engine, Sudden transmission failure after coolant contamination
Fix: Internal transmission cooler in radiator fails, mixing ATF and coolant. Requires new radiator, external transmission cooler install, full ATF flush (multiple cycles), often new valve body or full transmission rebuild if contamination severe. 8-12 hours if trans needs rebuild. Preventive external cooler install recommended on all W220s.
Estimated cost: $2,000-6,000
SBC (Sensotronic Brake Control) Hydraulic Pump Failure
Occasional · high severityTypical onset: 120,000-200,000 mi
Symptoms: 'STOP vehicle brake failure' warning, red brake light, Hard brake pedal, reduced braking assist, Loud humming/whining from ABS pump area, SBC fault codes stored in brake module
Fix: SBC hydraulic pump motor or accumulator fails. Mercedes discontinued support; requires used/reman SBC unit (~$1500-2500) or full conventional brake conversion (~$3000-4000 in parts). Pump swap is 4-6 hours, conversion is 10-14 hours. SBC units are getting scarce; budget for this proactively.
Estimated cost: $2,500-5,500
ABC (Active Body Control) Hydraulic Leaks and Pump Failure
Common · medium severityTypical onset: 100,000-180,000 mi
Symptoms: 'ABC visit workshop' warning, car drops to bump stops, Green hydraulic fluid leaks under vehicle (struts, lines, pump), Pump noise, grinding, whining during startup, Sluggish or uneven suspension response
Fix: ABC system uses high-pressure hydraulic fluid; struts, hoses, and pump seals fail. Individual strut replacement is 3-4 hours per corner ($1200-1800 each). Pump rebuild/replacement is 6-8 hours ($2500-4000). Pulsation damper failures add $800-1200. Full system overhaul can exceed $8000. Fluid must be changed every 30k miles religiously.
Estimated cost: $1,200-4,000
Fuel Injector and High-Pressure Fuel Pump Wear
Occasional · medium severityTypical onset: 150,000+ mi
Symptoms: Rough idle, black smoke, loss of power, Hard starting, extended cranking, misfires, Fuel in oil (dilution from injector leakage), Injector clicking/knocking noise at idle
Fix: OM613 common-rail injectors wear or seize in head; high-pressure pump can fail. Injector replacement 4-6 hours for set of 6 (must use Bosch OE or quality reman). HP pump replacement 3-4 hours. Injectors $1500-2400 set, pump $800-1200. Fuel filter changes every 10k miles critical to prevent premature wear.
Estimated cost: $2,000-3,500
Only buy if engine has been properly rebuilt or is verifiably low-mileage with perfect maintenance records, and budget $5k-8k for deferred SBC/suspension work — otherwise, run.
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.