2001 MERCEDES-BENZ S320 CDI W220

Typical onset: 80,000-150,000 mi

Symptoms: Sudden loss of power, heavy knocking or rattling from engine bay, Metal shavings in oil, low oil pressure warnings, Smoke from exhaust, engine seizure in worst cases, Often happens after extended highway runs or towing

Fix: OM613 suffers from inadequate piston cooling and weak crankshaft bearings. Failure typically destroys pistons, rings, rods, and bearings. Requires either full engine rebuild (30-40 hours labor) or short-block replacement (25-35 hours). Used engines are risky; professionally rebuilt units recommended. Includes machine work, all bearings, pistons, rings, gaskets, oil pump.

Estimated cost: $8,000-15,000

Typical onset: 100,000-180,000 mi

Symptoms: Deep knocking at idle that worsens under load, Oil pressure drops at operating temperature, Vibration through drivetrain, especially on acceleration, Metallic debris on oil drain plug magnet

Fix: OM613 crankshaft journals wear prematurely, leading to main bearing failure. Requires full engine disassembly, crankshaft removal, journal inspection/machining, new main and rod bearings, thrust washers. 28-38 hours labor. Crankshaft may need grinding or replacement if journals are scored beyond spec. Often combined with piston replacement if already apart.

Estimated cost: $6,500-12,000

Typical onset: 120,000-200,000 mi

Symptoms: White smoke from exhaust, coolant consumption without visible leaks, Oil in coolant reservoir or milky oil on dipstick, Overheating, especially under load, Rough idle, misfires if compression loss is severe

Fix: Head gaskets fail from thermal cycling and cooling system neglect. Inline-six has single head but gasket failure often warrants machining. Remove head, inspect for warpage, resurface if needed, new gasket, stretch bolts, timing chain verification. 18-24 hours labor. Should replace thermostat, coolant, and check injector seals while apart.

Estimated cost: $3,500-5,500

Typical onset: 80,000-140,000 mi

Symptoms: Transmission fluid dripping from undercarriage near radiator, Burnt transmission fluid smell, slipping shifts, Transmission overheating warnings on dash, Pink or red fluid mixing with coolant if internal cooler fails

Fix: 722.6 five-speed auto uses external and radiator-mounted oil coolers. Lines corrode, cooler tanks crack. External leaks require line replacement (2-4 hours). Internal cooler failure contaminates coolant and trans fluid—requires radiator replacement, full transmission flush, often torque converter replacement. 6-10 hours total for internal failure scenario.

Estimated cost: $800-3,200

Typical onset: 70,000-120,000 mi

Symptoms: Clunk or thud on shifts, especially reverse to drive, Vibration through center console at idle in gear, Driveline shudder on acceleration, Visible sagging or cracked rubber on mount inspection

Fix: Rear transmission mount (also called crossmember mount) absorbs diesel torque and fails from age. Replace mount, inspect crossmember bushings. 2-3 hours labor. Often done with front engine mounts for comprehensive fix. Requires transmission support during R&R.

Estimated cost: $450-750

Typical onset: 90,000-150,000 mi

Symptoms: Car sags overnight or after sitting, especially rear, Compressor runs constantly, cycling every few minutes, Suspension warning light, 'Stop vehicle too low' message, Uneven ride height side-to-side

Fix: Airmatic struts develop leaks at seals, compressor overworks and burns out. Strut replacement 3-4 hours per corner, compressor 4-6 hours including relay module check. Many owners convert to coil springs ($1,500-2,500) to avoid repeated air suspension costs. OE struts $600-1,200 each; compressor $800-1,400.

Estimated cost: $1,200-4,500

Typical onset: 100,000-180,000 mi

Symptoms: ABC warning light, 'Stop vehicle too low' message, car drops to bump stops, Whining or groaning from front suspension, especially on turns, Hydraulic fluid leaks at struts, lines, or pump, Stiff or harsh ride, loss of self-leveling function

Fix: If equipped with ABC (not all S320 CDI had it), system is maintenance-intensive. Pulsation damper, pump, struts, and accumulators all fail. Pump replacement 6-8 hours, struts 4-6 hours each, pulsation damper 3-4 hours. Fluid flushes required every 30k mi. Full system overhaul can exceed $10k. Coil conversion not available for ABC cars.

Estimated cost: $2,500-12,000

Symptoms: Hard starting, especially cold, long cranking before catch, Loss of power on acceleration, hesitation or stumbling, Rough idle, increased fuel consumption, Check engine light with lean or misfire codes

Fix: OM613 diesels are sensitive to fuel quality. Clogged filter causes low rail pressure, injector contamination leads to poor spray patterns. Filter replacement every 15k-20k mi (1 hour labor, $40-80 filter). Injector cleaning/replacement if contaminated: 6-10 hours for all six, $400-800 each for Bosch units. Preventive: fuel additives, quality diesel, frequent filter changes.

Estimated cost: $100-6,000