2004 MERCEDES-BENZ S320 CDI W220

Typical onset: 80,000-150,000 mi

Symptoms: Excessive black smoke on startup or acceleration, Sudden loss of power followed by severe knocking, Metal shavings in oil, low oil pressure warning, Seized engine or rod through block in worst cases

Fix: The OM613 is infamous for injector tip carbon buildup that breaks off, scores cylinders, and destroys bearings. Biodiesel accelerates this. Fix requires engine-out rebuild or short block replacement: 25-35 hours labor plus machine work. Many shops won't touch it—recommend reman long block.

Estimated cost: $8,000-15,000

Typical onset: 60,000-120,000 mi

Symptoms: Valve train noise, especially cold start ticking, Low oil pressure at idle when hot, Check engine light with camshaft position codes, Oil starvation damage to head components

Fix: Extended service intervals and wrong-spec oil cause sludge in the head. Cam lobes wear, followers collapse. Head removal, cleaning, cam replacement, and new followers: 18-24 hours. Often found during diagnosis for other engine issues.

Estimated cost: $4,500-7,500

Typical onset: 70,000-130,000 mi

Symptoms: Vehicle sagging on one or both corners overnight, Airmatic warning light with 'Visit Workshop' message, Compressor runs constantly or won't run at all, Harsh ride or excessive body roll

Fix: Air struts leak at 100k-ish, compressor valve blocks fail, level sensors corrode. Each strut: 2-3 hours. Compressor: 3-4 hours. Full system overhaul (all four struts + compressor): 12-15 hours. Many convert to coils for $1,500-2,500.

Estimated cost: $800-1,200 per strut, $1,800-2,800 compressor, $4,500-6,500 all four corners

Typical onset: 90,000-150,000 mi

Symptoms: Harsh or delayed shifts, especially 2-3 and 3-4, Limp mode with P0715 or P0700 codes, Slipping under load or no movement in gear, Transmission fluid overheating

Fix: The 722.6 transmission's 13-pin conductor plate cracks solder joints; valve body solenoids stick. Pan drop, valve body R&R, new conductor plate and fluid: 8-10 hours. If clutches are burnt from slipping, add rebuild: 18-22 hours total.

Estimated cost: $1,800-3,200 conductor plate/valve body, $4,500-6,500 full rebuild

Typical onset: 80,000-140,000 mi

Symptoms: Red 'BRAKE VISIT WORKSHOP' warning with gong, Hard brake pedal or complete loss of power assist, ABS/ESP lights on, traction control disabled, Whining or buzzing from under hood near firewall

Fix: The hydraulic brake-by-wire pump fails (motor or accumulator). Mercedes discontinued new units; reman/exchange only. Remove and replace pump: 4-6 hours. Must be coded to car. This is a known W220 ticking time bomb.

Estimated cost: $2,500-4,000

Typical onset: 100,000-180,000 mi

Symptoms: Hard starting, long cranking, white smoke, Rough idle, misfires on one or more cylinders, Poor fuel economy, loss of power under load, Metal contamination in fuel filter

Fix: Bosch common-rail injectors seize or leak internally; high-pressure pump cam wears. Injectors: 6-8 hours for all six (must remove intake). HP pump: 5-7 hours. If metal in system, flush rails and replace all injectors plus pump.

Estimated cost: $3,500-5,500 injectors, $1,800-2,800 HP pump, $6,000-9,000 full system

Typical onset: 80,000-140,000 mi

Symptoms: ABC warning light, 'Car Too Low' message, Green hydraulic fluid puddles under car, Harsh ride, clunking over bumps, Pump running excessively, whining noise

Fix: If equipped with ABC (some S320 CDI have airmatic instead), hoses, accumulators, and pulsation dampeners leak. Each front strut: 4-5 hours. Rear: 3-4 hours. Pump: 6-8 hours. This system is a money pit; budget $10k+ for full repair.

Estimated cost: $1,200-2,000 per strut, $2,500-4,000 pump, easily $8,000-12,000 for comprehensive repair