Mercedes-Benz S 600
The last naturally aspirated V12 from Mercedes before the switch to the biturbo era with the M275. The M137 uses SOHC valve actuation with three valves per cylinder — two intake, one exhaust — an architecture Mercedes pursued nowhere else with such consistency. A hydraulic-electric cylinder deactivation system (CDA) was fitted to save fuel; when it fails the CDA valves shut off half the cylinder bank. The same applies to the two encapsulated ignition module banks — completely inseparable, non-repairable, and expensive to replace. A well-maintained M137 delivers one of the smoothest engine notes imaginable: silky, uniform, inaudible at motorway speeds. The price is a maintenance burden that is not for tight budgets.
Floating V12 Sensation in Its Purest Form
367 hp from 5.8 litres of naturally aspirated V12 means no sport, but something rarer: absolutely effortless propulsion without any strain. At 130 km/h the M137 turns so unhurriedly that one forgets a twelve-cylinder is working. No turbo, no step change, just an endlessly even surge.
Engine Weaknesses 6
The hydraulic-electric ZAS cylinder deactivation valves fail with increasing age. Suddenly only 6 cylinders are active, MIL illuminates. Repair costs approx. 880 EUR per valve.
Symptoms: Engine runs rough with strong vibration, significant power loss, check engine light, faults P0307–P0312
The two ignition module banks (one per cylinder bank) fail after 10–15 years — often in quick succession. Fully potted components, not repairable; OEM replacement approx. 1,400 EUR each.
Symptoms: Severe power loss, rough engine, multiple cylinder misfire codes P0300–P0312, fuel smell from exhaust
At high mileage cylinder bore walls become oval, oil enters the combustion chamber. Consequential costs from contaminated lambda sensors and catalytic converters are extremely high.
Symptoms: Blue smoke on start, steadily increasing oil consumption (>0.5 L/1,000 km), contaminated lambda sensors
The oil-water heat exchanger sitting in the V-valley becomes leaky and loses oil at the rear of the engine. Access requires extensive disassembly, so labour costs are high.
Symptoms: Oil spots under the vehicle, oil loss without visible external leak, oil smell after parking
The 12 individual ignition coils on the V12 fail one after another. With 12 cylinders this means frequent workshop visits. Prophylactic replacement of all coils recommended.
Symptoms: Misfires, rough running, check engine light P0301–P0312
M137 V12 is prone to oil loss: valve cover gaskets and sump gasket wear typically. 1–1.5 L oil consumption per 1,000 km is considered acceptable.
Symptoms: Oil smell in engine bay, oil spots under vehicle, dropping oil level.
Vehicle Weaknesses 6
The Airmatic compressor runs continuously when there are leaks in the system and burns out. Without swift intervention, total suspension failure and blocked ride-height control follow.
Air spring bag seals age and become leaky. The vehicle drops on one side or completely. All four struts typically need replacement by around 250,000 km.
Three SAM modules in the engine bay and interior are vulnerable to water ingress through blocked drain channels. Secondary damage can exceed the vehicle's residual value.
The hollow-section sills of the W220 rust from the inside out. Nothing is visible externally for a long time until the rust is already well advanced. Pre-facelift models (1998–2002) are particularly affected.
The W220 rusts at the underbody, wheel arches and weld seams, particularly where underbody protection has not been renewed regularly.
Electric window regulators are not rated for the weight of the W220 double-glazed windows and wear out prematurely. Driver's side particularly affected.
Reports & Tests
289 owner complaints filed with NHTSA (1998–2005). Most reported: Electrical (108), Suspension (68), Lighting (24).