Mercedes-Benz SL 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.
V12 open — sounds like a deep-sea vessel on the motorway
The roof opens and the V12 awakens with a dry twelve-piston snarl. At full throttle it pins the driver deep into the seat — 517 hp in a 1,800 kg roadster. No turbo lag, just even force from 1,500 rpm. The ABC chassis keeps the cabriolet planted. The SL 600 is the rare combination of roadster feel and grand-tourer composure. Anyone asking about fuel consumption is buying the wrong car.
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 11
The ABC hydraulic pump can develop cracks and lose pressure from 120 bar down to 60 bar. Suspension can no longer maintain ride height, soft and vague handling characteristics.
The hydraulic fluid absorbs moisture, rubber components decompose and contaminate the system. Valve block and lines develop leaks. Annual oil change prevents major damage.
The SBC unit is designed for approximately 400,000 brake cycles and fails at this point. When it fails, braking effectiveness is severely reduced — a safety risk. Mercedes extended the warranty to 25 years.
The electric motor of the roof pump burns out. Windings and circuit board affected. Pump runs audibly for longer or not at all. Specialist repair from 595 EUR, Mercedes dealer significantly more expensive.
Defective control unit causes functional failures of the vario roof. Roof stops in various positions, headrests raise but do not return.
The electric folding roof develops problems with limit switches and hydraulic components. When the sequence is disrupted, the roof no longer opens or closes.
The R230 develops clicking and creaking noises in the steering rack, often at every third steering input or under load. Track rod ends are a frequent cause. The steering rack can also lose hydraulic oil.
Typical rust spots develop at the tips of the rear quarter panels at the transition to the door and sill. Moisture and dirt collect there. Rust can grow from the inside out and is often only visible at a late stage.
The Vario roof contains 11 hydraulic cylinders. The seals become porous with age; escaping oil damages trim panels and the boot. Seal sets for all cylinders are available for around 99 EUR.
Despite the hardtop, water enters the boot. Porous seals at the interlocking points of the Vario roof as well as blocked drainage channels at the rear screen.
The plastic hinges on the side parcel shelf flaps become brittle after approximately 15 years and snap off. OEM replacement around 1,600 EUR for both sides, a brass repair kit is available for around 90 EUR.
Reports & Tests
275 owner complaints filed with NHTSA (2001–2012). Most reported: Suspension (77), Brakes (73), Electrical (41).