Mercedes-Benz CLS 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.
Supercharged Design Icon — More Muscle Than the 63
476 hp in the most beautiful four-door car of the 2000s. The CLS55 sounds deeper and more massive than the CLS63 successor — less emotional, but more muscular. 0–100 in 4.7 seconds; 1.9 tonnes become an extremely fast touring saloon in a coupé body. Steering too disconnected for a sporty vehicle — the CLS is a GT, not a sports car. Cheaper brake discs than the 63 (€240 vs. €1,600 per pair). Fuel consumption: up to 40 litres in 30 minutes has been documented.
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 7
Airmatic with defective air tanks, compressor failures and leaking air springs. Front dampers approximately €700 each. Frequent money pit.
Early CLS models up to 2005 with SBC brakes: a defective pump can reduce brake pressure and increase stopping distance. Recall issued.
AIRMATIC air suspension on the C219 is highly wear-prone. The compressor has several failure points; air spring bellows fail with age.
Early C219 CLS (up to 2006) with SBC hydraulic brake — failure-prone, expensive to maintain. Mercedes replaced SBC with a conventional brake in 2006.
Wiring break means the boot cannot be unlocked via remote control. Boot interior light and number plate lighting also fail.
Three-way valve of the 4-zone automatic climate control fails; rear zone only receives warm air.
COMAND infotainment is prone to frequent crashes, freezing and complete failures. System is outdated and difficult to repair — reboot often the only fix.
Reports & Tests
179 owner complaints filed with NHTSA (2004–2010). Most reported: Fuel System (61), Brakes (32), Fuel System (29).