Mercedes-Benz CL 600
Twelve cylinders, two turbochargers, a V-valley layout — technically fascinating and maintenance-intensive in equal measure. The fully encapsulated ignition module system with two banks at 1,400 EUR each is the most well-known cost factor; failure of both banks usually follows in quick succession. The oil-water heat exchanger in the V-valley almost always leaks eventually — factor in engine removal for the repair. The four camshaft solenoids fail to seal reliably after 80,000–100,000 km; oil creeps into the wiring harness and corrodes control units. Both turbochargers sit deep under the engine bay — removal and installation costs more than the turbo itself. Runs without issue beyond 300,000 km with diligent maintenance; what kills it is deferred servicing. Purchase requirement: complete service history, documented wiring harness check, no ABC alarm backlog, fresh ignition modules.
Most Elegant V12 Coupé of Its Era — No Tantrums
500 hp in the C215 CL coupé: the V12 gives the heavy body a lightness no V8 replicates. No frenetic revving — the pressure comes from the bottom and stays. The gearbox shifts unobtrusively. The CL 600 is the more refinedly-sounding counterpart to the SL 55 AMG — less aggressive, more diplomat. ABC hydraulics and ignition module banks will inevitably accompany every long-term owner.
Engine Weaknesses 9
Both ignition module banks are fully potted wear items with a typical service life of 10–15 years. Failures tend to follow each other quickly. OEM cost approximately €1,400 each.
Symptoms: Jerking and power loss, rough running, misfire codes P0307–P0312, petrol smell from the exhaust
The two turbochargers show bearing and wastegate wear at high mileage. Engine removal is required for replacement; repair costs €2,000–4,000 per turbo.
Symptoms: Whistling or rattling turbo noises, power loss under hard acceleration, blue smoke from oil loss
The M275 V12 Biturbo in the S600/CL600 puts extreme stress on the engine mounts due to its weight (>300 kg engine). At the same time, the ABC hydraulic lines age and leak. Both issues frequently occur together.
Symptoms: ABC suspension hydraulic oil loss, engine sitting lower, vibrations in the cabin, ABC warning message
On the M275 V12 with 4 camshafts, all 4 solenoids are affected. Oil leaking into the wiring harness leads to ECU corrosion. Repair is especially labour-intensive on the V12.
Symptoms: Cold-start rattle, camshaft adjuster fault codes bank 1+2, oil traces on connectors, in extreme cases engine ECU failure
Wiring harness insulation in the engine bay becomes brittle after 10–15 years from heat. Affected: injector, MAF and throttle body wiring. Short circuits in the MAF harness can destroy the engine beyond repair.
Symptoms: Sporadic misfires, MAF fault codes, ignition misfires without clear cause, in extreme cases engine failure and fire risk.
The integrated contact plate (TCM) in the 7G-Tronic fails due to heat damage at the speed sensors. Gearbox shifts jerkily, then not at all. New plate requires SCN coding at an authorised dealer.
Symptoms: Delayed, jerky gear changes, gearbox stuck in 2nd gear (limp mode), fault codes P0717/P0718 transmission control unit.
The oil-water heat exchanger seal in the V-valley becomes leaky. Engine removal is required for repair, so total costs reach €1,700–2,500 despite the cheap parts.
Symptoms: Oil loss without a clearly visible leak, oil spots after extended parking, occasionally oil in the coolant reservoir
The separate intercooler cooling circuit loses coolant through ageing hoses and O-rings. Retrofit fix: the M279 expansion tank fits as a direct swap.
Symptoms: Dropping coolant level in the expansion tank, overheating warning on extended motorway runs, power reduction
Valve stem seals harden and piston rings wear with increasing mileage. 12 cylinders mean 48 valve stem seals. Oil consumption rises noticeably from 150,000 km — up to 1 L/2,000 km.
Symptoms: Blue smoke after prolonged idle, dropping oil level between service intervals, carbon deposits on spark plugs.
Vehicle Weaknesses 6
The ABC hydraulic suspension on the C215 is the most expensive weak point. Each axle has a valve block (approximately €1,000 without fitting). Contaminated hydraulic oil damages the proportional valves.
Blocked drainage channels allow water ingress under the glove box. Several control units are located there and suffer permanent damage.
The two valve blocks of the ABC suspension wear through hydraulic contamination. Once the vehicle immediately sags after being switched off, the valve block is defective. Delayed intervention leads to pump and line damage.
On the C215, rust bubbles form preferentially on door lower edges and the C-pillar. Early models up to 2004 particularly affected.
Up to 30 wires in the wiring harness between door and body break through constant flexing after approximately 120,000 km. Window regulators, central locking, seat adjustment and SoftClose on the driver's door are affected.
The NTC interior temperature sensor in the ceiling light housing fails and tells the climate control that the cabin is at 0 °C. The heater then blows maximum hot air permanently.