Mercedes-Benz AMG S 63
5.5-litre V8 BiTurbo — AMG's first forced-induction V8 and the successor to the naturally aspirated M156. 525–585 hp depending on model, up to 900 Nm in the S version. The character is fundamentally different from the M156: instead of a high-revving scream, a brutal torque wave from 1,750 rpm. The sound is deeper, more bass-heavy, with a characteristic turbo hiss on lift-off. Less emotional than the naturally aspirated engine, but in a different league on the motorway — above 200 km/h the M157 still accelerates like others do at 100. Timing chain is the known Achilles heel: chain tensioner failure at 80,000–120,000 km, Mercedes has improved the design (non-return valve in cylinder head oil gallery). Piezo injectors are sensitive to fuel quality, service life 100,000–150,000 km. Turbos last 200,000+ km with proper warm-up and cool-down — shut off immediately after a motorway run and they'll fail significantly earlier. Warm up the engine, allow cool-down after hard use, oil changes every 10,000 km with 0W-40 — then 300,000 km is realistic.
First BiTurbo in the S-Class — 544 hp Understatement
S 63 AMG W221: first AMG with BiTurbo V8 instead of a naturally aspirated engine. 544 hp and 800 Nm from 2,000 rpm — effortlessly fast on the motorway, the M157 murmurs unobtrusively in the background. The S-Class makes the AMG performance invisible: a chauffeur's car that dusts off 300-series Ferraris when needed. Airmatic ageing and W221 electronics as ongoing costs.
Engine Weaknesses 11
The timing chains on the M157 5.5L BiTurbo V8 stretch, especially on vehicles with frequent cold starts and short trips. Engine damage possible if chain jumps. Extensive repair on the V8.
Symptoms: Metallic rattling on cold start, camshaft position fault codes, rough running, in extreme cases engine damage
Under heavy use the piston rings on the M157 wear prematurely. Oil consumption above 1 L/1,000 km is possible. Engine overhaul required with advanced wear.
Symptoms: Rising oil consumption, blue smoke on acceleration, oil mist from exhaust, oil level warnings
The high-pressure fuel pump on the M157 can wear internally at high mileage. Pressure drop in the rail causes difficult starting and power loss.
Symptoms: Difficult starting, power loss under load, hesitation at high rpm, fuel pressure fault codes
The M157 is affected by known timing chain wear from 80,000–120,000 km. Mercedes retrofitted check valves in the oil supply passages (TSB LI05.20-P-057028).
Symptoms: Rattling on cold start, later also at idle, check engine light with camshaft fault codes, power loss
The oil pump gear on the M157 wears at high rpm and generates metal debris. Oil pressure drop leads to overheating and cylinder bore damage.
Symptoms: Oil pressure warning at high rpm, metallic knocking from lower engine, heavy oil consumption
Timing chain and tensioners wear prematurely, especially model years 2011–2013. Mercedes retrofitted a check valve in the oil passages of the cylinder head. Repair often in the four-figure range, worst case five figures.
Symptoms: Rattling on cold start, later also at idle, increased on acceleration; check engine light
The valve cover gaskets on the M157 V8 leak and allow oil to drip onto the hot turbochargers. Smoke and a burning smell are the result.
Symptoms: Oil smell and smoke from engine bay, oil drops visible on turbochargers, dropping oil level
The M157 uses Bosch piezo injectors that typically last 100,000–150,000 km. Aftermarket alternatives are not available.
Symptoms: Rough engine, uneven idle, elevated fuel consumption, individual cylinder fault codes
Electric auxiliary water pump for charge air cooling fails. Leads to reduced power in limp mode.
Symptoms: Power loss under high load, warning message on display, limp mode
Bosch piezo-ceramic injectors are sensitive to fuel quality and have a limited service life of approx. 100,000–150,000 km. Replacing all 8 injectors costs up to 3,000 EUR; repair is not possible.
Symptoms: Rough running, misfires, power loss, check engine light, poor cold-start behaviour
The wastegate flaps on both turbochargers rattle at cold start due to play in the linkages. Usually an acoustic issue only, rarely performance-related.
Symptoms: Metallic clattering on cold start for 1–2 minutes, disappears at operating temperature
Vehicle Weaknesses 6
The air struts of the W221 wear over time. Between 200,000 and 300,000 km, all four struts typically need replacement.
The Airmatic pressure reservoir tanks at the rear axle can corrode. Removal requires disassembly of the rear axle.
The instrument cluster develops pixel faults due to detached ribbon cables. In worst case, complete display failure.
The W221 shows sporadic CAN bus communication faults leading to failures of various systems: ESP, headlight control, fog lights.
Air spring bags (usually rear) become leaky and lose pressure gradually. The vehicle then sits 3–4 cm lower on one side. Fault code 5285 (fill process too long) appears. Repair is only possible by replacement.
The W221's extensive comfort electronics are fault-prone: electric windows, door mirrors and the optional panoramic sunroof show failures due to aged connectors and control units.
Reports & Tests
233 owner complaints filed with NHTSA (2005–2013). Most reported: Electrical (63), Engine (41), Powertrain (35).