Mercedes-Benz SL 55 AMG Kompressor
5.4-litre V8 with Eaton Lysholm twin-screw supercharger — the legendary 'Kompressor' AMG. 476–500 hp depending on model, 700+ Nm from 2,650 rpm. The sound is unmistakable: a deep V8 rumble overlaid with the characteristic supercharger whine under load — at full throttle a mechanical scream that's instantly addictive. Torque arrives like a wave: gently swelling then brutal. No turbo lag, no throttle delay — the supercharger delivers boost from idle. Tuning potential is enormous: a pulley swap (83 mm instead of 87 mm) adds 40–50 hp at the rear wheels, and the community has pushed the engine beyond 800+ hp. Critical maintenance points: supercharger magnetic clutch (check air gap 0.35–0.45 mm), charge air cooler pump (low-temperature circuit), rear crankshaft seal. Oil changes with 0W-40 every 10,000 km. Pre-2004 engines had more teething problems — noticeably more mature from 2004. One of the most robust AMG engines ever built when maintained properly.
The Catapult — Blown V8, Roof Down, No Radio
On a cold start with a cold exhaust system: priceless. In the lower range a deep booming, in the mid-range hissing, at full throttle like roaring lions and bears. The radio is superfluous with the roof down — every brass note from the force-fed V8 demands to be heard. Whether cruising or pinning the throttle, above 200 km/h there seems to be no end: a ride on a cannonball. ABC dampers at €1,000 each are the downside. An engine like this will never exist again.
Engine Weaknesses 9
The Eaton supercharger bearings wear after 100,000+ km — mechanical noise increases, in worst case the supercharger seizes. Check supercharger oil (120–130 ml) regularly. Replacement supercharger from 1,200 EUR, complete with installation 2,500–3,500 EUR.
Symptoms: Increasing mechanical whining/howling from the supercharger even at low rpm, metallic grinding under load, supercharger oil loss.
Coolant hoses become brittle after 10+ years and can burst without warning — particularly critical on a supercharged V8 with high heat rejection. Thermostat occasionally sticks open. Complete coolant hose set as prevention from 60,000 km recommended.
Symptoms: Coolant temperature rises above 100°C, coolant steam under the bonnet, coolant loss, sweet smell from vents.
The Eaton supercharger magnetic clutch wears over time — friction material wears, supercharger sporadically fails to engage. Air gap (clearance) must be 0.35–0.45 mm; above 0.8 mm the clutch no longer engages reliably. Aftermarket pulley modifications worsen the problem if air gap is not correctly set.
Symptoms: Sporadic power loss at full throttle, supercharger does not engage (no supercharger whine audible), EPC fault message in instrument cluster, releasing and re-applying throttle helps briefly.
The separate low-temperature coolant pump for the charge air cooler fails — charge air temperature rises, engine loses noticeable power under sustained load. No engine damage, but frustrating power loss especially in summer and on motorways.
Symptoms: Creeping power loss with warm engine under sustained load, charge air temperature rises above 60°C (visible on scan tool), no fault message — only subjectively less power.
The rear crankshaft seal becomes leaky over time — oil drips onto the gearbox flange. Repair requires gearbox removal, hence high labour cost. Best combined with another gearbox service.
Symptoms: Oil spot under the vehicle at the bell housing, visible oil film at the engine/gearbox interface, slightly rising oil consumption.
The OEM crankshaft pulley has a rubber damper that detaches after 80,000+ km — belt jumps, engine stops. Aftermarket steel/aluminium pulleys (e.g. Fluidampr, NS Custom) as a permanent solution. Due anyway with a pulley modification.
Symptoms: Squeaking noises from the belt drive, visible belt misalignment at the crankshaft pulley, pulley wobbles on visual check.
Rubber engine mounts wear faster than on the naturally-aspirated M113 due to the higher torque (700+ Nm). Torn mounts cause noticeable vibrations at idle and stress the driveshafts and gearbox. Preventive replacement every 60,000–80,000 km.
Symptoms: Vibrations at idle felt at steering wheel and gear lever, dull thudding on throttle on/off, engine visibly moves when revving.
The 8 ignition coils and ignition leads age faster than on the naturally-aspirated M113 due to the higher thermal load of the supercharged engine. Balance deviations >3.5 per cylinder indicate ignition problems. Replace all 8 at the same time; Bosch quality recommended.
Symptoms: Rough idle, cylinder balance deviation >3.5 on balance test, misfire fault codes P0300–P0308, slight hesitation at part throttle.
Various vacuum hoses and the fuel tank vent hose become brittle and fall off — false air causes rough idle and hesitant pull-away. Often overlooked because symptoms are subtle and the engine runs normally under load.
Symptoms: Hesitant pull-away below 1,500 rpm, rough idle after warm-up, hissing from engine bay at idle, sporadic power fluctuations.
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).