The 2009 E55 AMG (W211 chassis, M113K engine) is a supercharged beast known for solid drivetrain reliability when maintained, but suffers from age-related issues with airmatic suspension, transmission mounts, and the critical SBC brake system. The M113K engine itself is stout, but neglect or poor maintenance can lead to catastrophic internal failures.
SBC (Sensotronic Brake Control) System Failure
Common · high severityTypical onset: 80,000-150,000 mi or 10+ years regardless of miles
Symptoms: Red brake warning light with 'Visit Workshop' message, Complete loss of power brake assist, ABS/ESP malfunction warnings, Hard brake pedal or unpredictable brake response
Fix: SBC pump replacement is mandatory when it fails; Mercedes issued a recall extending warranty to 25 years/250k miles but that expired in 2020. Requires specialized programming and bleeding procedure, 4-6 hours labor for experienced tech. Some owners convert to conventional brake system.
Estimated cost: $2,500-4,000
Airmatic Suspension Failure (Air Struts and Compressor)
Common · medium severityTypical onset: 70,000-120,000 mi
Symptoms: Vehicle sits low, especially after sitting overnight, Airmatic warning on dash, Compressor runs constantly or doesn't run at all, Uneven ride height side-to-side, Clunking from suspension when going over bumps
Fix: Typically one or more air struts develop leaks in the rubber bellows. Compressor failure also common. Strut replacement is 2-3 hours each corner, compressor adds 2-3 hours. Many owners convert to coilover conversion kits to eliminate future issues.
Estimated cost: $1,200-2,500 per strut OE; $2,500-3,500 for compressor; coilover conversion $2,000-3,000 installed
Transmission Mount and Conductor Plate Failures (722.6 Trans)
Common · medium severityTypical onset: 60,000-100,000 mi
Symptoms: Harsh shifting or delayed engagement into gear, Clunk when shifting from Park to Drive/Reverse, Limp mode with transmission fault codes, Erratic shifting patterns, Visible fluid leak from bell housing area
Fix: Transmission mounts fail from the torque of the supercharged V8, causing harsh engagement. Conductor plate (internal wiring harness) also fails causing erratic shifts. Mount replacement is 2-3 hours; conductor plate requires trans removal and internal work, 12-16 hours total labor.
Estimated cost: $400-800 for mounts; $2,500-4,500 for conductor plate with fluid/filter service
M113K Engine Internal Failure (Piston/Bearing Damage)
Occasional · high severityTypical onset: 100,000-150,000 mi or from neglect at any mileage
Symptoms: Knocking or ticking noise from engine, especially on cold start, Metal shavings in oil or on magnetic drain plug, Loss of oil pressure, Rough running or misfires, Catastrophic failure with loss of power
Fix: M113K is generally bulletproof, but oil starvation from extended drain intervals or running low causes bearing and piston failure. Once internals are damaged, requires full engine teardown. Short block replacement is 25-35 hours; full rebuild with machine work is similar. Many opt for used low-mile engines.
Estimated cost: $8,000-15,000 for rebuild or short block; $6,000-9,000 for used engine swap
Supercharger Intercooler Pump Failure
Occasional · medium severityTypical onset: 80,000-130,000 mi
Symptoms: Reduced power output and boost, Engine runs hotter than normal, Coolant leak from front of engine, Warning light for intercooler system
Fix: The intercooler cooling pump (separate from main coolant system) fails, reducing supercharger efficiency. Replacement is 2-3 hours, involves front bumper removal for access. Original pumps are prone to failure; aftermarket upgrades available.
Estimated cost: $600-1,200
Crankshaft Position Sensor and Camshaft Position Sensor Failures
Occasional · medium severityTypical onset: 60,000-120,000 mi
Symptoms: Random stalling or no-start condition, Rough idle and misfires, Check engine light with crank/cam correlation codes, Engine cranks but won't fire
Fix: These sensors fail from heat exposure over time. Crank sensor is accessible in 1-1.5 hours; cam sensors are behind timing covers requiring more disassembly, 3-4 hours each bank. Often both are replaced preventatively.
Estimated cost: $300-600 for crank sensor; $800-1,400 for both cam sensors
Transmission Oil Cooler Leaks
Occasional · medium severityTypical onset: 90,000-140,000 mi
Symptoms: Transmission fluid dripping from front of vehicle, Pink or red fluid mixing with coolant in expansion tank, Transmission overheating, Milky appearance in transmission fluid
Fix: External oil cooler or internal radiator-mounted cooler develops leaks. External cooler replacement is 2-3 hours; internal requires radiator removal and trans flush, 4-6 hours. Cross-contamination of coolant and trans fluid can destroy transmission if not caught early.
Estimated cost: $800-1,500 including full fluid flush
Buy one if maintenance records are solid and you have a $3-5k buffer for SBC/Airmatic; the M113K drivetrain is bulletproof with care, but neglected examples are money pits—this is a $70k car when new that demands respect and proper upkeep.
AI-assisted summary drawn from NHTSA recall data, our labor-times database, and platform knowledge. Not a substitute for a pre-purchase inspection on a specific vehicle.