1998 MERCEDES-BENZ S-CLASS

Typical onset: 80,000-120,000 mi

Symptoms: Vehicle sagging on one or more corners after sitting overnight, Suspension warning light illuminated, Compressor runs constantly or not at all, Harsh ride quality or bottoming out

Fix: Struts leak internally and compressor wears out. Replace all four struts plus compressor and accumulator for longevity. 6-8 hours labor. DIY strut conversion kits to conventional springs exist but affect ride quality.

Estimated cost: $3,000-5,500

Typical onset: 60,000-150,000 mi

Symptoms: Intermittent stalling or no-start conditions, Multiple seemingly-unrelated electrical faults and check engine lights, Engine misfire codes on multiple cylinders, Sticky residue visible on engine harness insulation

Fix: Mercedes used soy-based insulation that literally rots into goo. Engine harness replacement is 12-16 hours on V8s, 20+ hours on V12s. Transmission harness adds another 8-10 hours. Cannot be reliably patched—needs full replacement.

Estimated cost: $2,500-6,000

Typical onset: 100,000-150,000 mi

Symptoms: Harsh or delayed shifts, especially 2-3 and 3-4, Limp mode activation with transmission fault codes, Slipping between gears under acceleration, No movement in drive or reverse

Fix: The 13-pin connector on the conductor plate cracks and causes erratic operation. Valve body wears internally. Requires pan drop, valve body removal and rebuild or replacement, new conductor plate. 8-10 hours labor. Oil cooler lines often leak simultaneously—address together.

Estimated cost: $2,000-3,500

Typical onset: 90,000-140,000 mi

Symptoms: Rough idle and stumbling under load, Random misfire codes across multiple cylinders, Hard starting when engine is hot, Poor fuel economy and loss of power

Fix: Beyond harness rot, ignition coils and distributor caps crack. Ovator system on V12s fails expensively. Budget coil packs for all cylinders, cap/rotor, plus plug wires. V12 needs 4 distributors vs 2 on V8. 6-8 hours labor for comprehensive ignition refresh.

Estimated cost: $1,800-4,200

Typical onset: 70,000-110,000 mi

Symptoms: Excessive vibration at idle in drive, Clunking when shifting into gear, Visible oil leaking from mount housing, Engine rocks excessively during acceleration

Fix: All three or four mounts (depending on engine) leak hydraulic fluid and collapse. Front and rear are straightforward, transmission mount requires transmission support. 4-6 hours for all mounts. Use OE or Lemforder—aftermarket fails quickly.

Estimated cost: $1,200-2,000

Typical onset: 80,000-130,000 mi

Symptoms: Intermittent no-start, especially when engine is hot, Stalling while driving with no warning, Tachometer drops to zero while running, Engine cranks but refuses to fire

Fix: Heat causes sensor failure. CPS is buried behind timing cover on some engines—requires front cover removal on M120 V12 (14+ hours). V8s easier at 2-3 hours. Replace both cam sensors simultaneously. Keep a spare CPS in the glovebox on V12 cars.

Estimated cost: $400-3,500

Symptoms: No heat or stuck on full heat regardless of setting, Blower motor inoperative or stuck on one speed, Climate control display blank or flickering, Coolant smell in cabin with wet passenger carpet

Fix: Push-button climate module fails internally—$400-800 for rebuilt unit plus 2 hours coding. Heater control valves stick closed or leak into cabin. Valve replacement 3-4 hours due to dashboard access. Auxiliary water pump also fails, leaving rear passengers without heat.

Estimated cost: $800-1,800

Symptoms: Any repair takes 2-3x longer than V8 equivalent, Specialized scan tools required for proper diagnostics, Parts availability poor and costs double V8 pricing, Mechanics refuse to work on them

Fix: The 6.0L V12 is two M119 inline-6 engines married together with catastrophic parts pricing. Simple jobs become epics—spark plugs are 4 hours, anything behind the timing covers is 20+ hours. Wiring harness rot is doubly expensive. Find a specialist or budget $200+/hour shop rates.

Estimated cost: n/a - expect 2-3x V8 costs