2002 MERCEDES-BENZ S600

Typical onset: 80,000-150,000 mi

Symptoms: Car drops to the ground when parked (ABC struts leaking), Rough ride, bottoming out over bumps, ABC warning light with 'car too low' message, Whining or groaning from hydraulic pump, Fluid leaks under car (green Pentosin CHF 11S)

Fix: ABC struts seal internally and leak down. Front struts run $800-1,200 each, rears $1,000-1,500 each. Pump replacement is 4-6 hours labor. Pulsation damper (common failure) is 2 hours. Many owners face replacing multiple struts simultaneously plus the pump accumulator. Full system rebuild with all four struts, pump, and damper can hit 20+ hours at a specialist.

Estimated cost: $3,000-12,000

Typical onset: 90,000-140,000 mi

Symptoms: Compressor runs constantly or cycles frequently, Car sags in rear overnight, Airmatic warning light, Loud compressor noise from right rear wheel well, Uneven ride height side-to-side

Fix: If equipped with Airmatic instead of ABC (some markets), the compressor fails from overwork when struts leak. Compressor replacement is 3-4 hours. Struts are $400-700 each, 2-3 hours per corner. Relay valve (distribution block) also fails and costs $300-500 plus 2 hours labor.

Estimated cost: $1,500-4,500

Typical onset: 100,000-180,000 mi

Symptoms: Harsh or delayed shifts, especially 2-3 or 3-4, Transmission slipping or flaring on upshifts, Limp mode (stuck in one gear), Check engine light with P0715, P0720 speed sensor codes, Erratic shifting when cold, improves when warm

Fix: The 5-speed 722.6 transmission has a conductor plate (13-pin connector plate) that fails from heat and fluid contamination. Replacement requires pan drop, valve body removal, about 6-8 hours labor. Often done with new valve body if solenoids are scored. Cooler lines and external cooler also fail, leading to fluid contamination.

Estimated cost: $2,000-4,500

Typical onset: 60,000-120,000 mi

Symptoms: Random misfires on multiple cylinders, Rough idle, hesitation, or stalling, Check engine light with multiple oxygen sensor codes, Engine runs worse in damp or hot weather, Visible cracked or deteriorated insulation on wires

Fix: Mercedes used soy-based insulation that biodegrades with heat and rodent damage. Affects both engine harness and transmission harness. Engine harness replacement on V12 is 12-18 hours due to packaging. Some techs repair sections, but full replacement is recommended. Transmission harness adds another 4-6 hours.

Estimated cost: $3,500-7,000

Symptoms: Windows won't operate or operate erratically, Interior lights stuck on or won't turn on, Door locks cycle on their own, Wipers, turn signals, or other accessories dead, Battery drain overnight

Fix: Signal Acquisition Module (front and rear SAM units) control most electrical functions. They fail from water intrusion or solder joint cracks. Replacement is 2-3 hours each, but requires dealer programming. Used modules need VIN coding. Front SAM is under dash driver's side, rear SAM is in trunk.

Estimated cost: $800-2,500

Typical onset: 40,000-80,000 mi

Symptoms: Check engine light with misfire codes (P0300-P0312), Rough idle, especially when cold, Hesitation or stumble on acceleration, Reduced fuel economy, One or more cylinders misfiring

Fix: The M137 has 12 coils, and they fail progressively. Coils run $80-150 each. Access requires removing intake plenum covers. Plan on 4-6 hours to do all 12 coils and plugs as a preventive set. Plugs must be gapped correctly (.039-.043") and torqued to 18-22 ft-lbs or they'll crack the threads.

Estimated cost: $1,200-2,200

Typical onset: 80,000-140,000 mi

Symptoms: Battery light on dash, Charging voltage erratic (below 13.5V or above 15V), Battery repeatedly goes dead, Electrical accessories dim or flicker, New battery doesn't solve the problem

Fix: The W220 S600 uses a 210-amp alternator with external voltage regulator. Regulator fails more often than alternator itself. Regulator replacement is 1.5-2 hours. Full alternator is 3-4 hours due to V12 packaging and removal of accessory drive components. Remanufactured alternators often fail quickly; OE Bosch is best.

Estimated cost: $600-1,800