2008 MERCEDES-BENZ CLS55 AMG

Typical onset: 80,000-120,000 mi

Symptoms: Metallic knocking or ticking from lower engine that worsens with RPM, Oil pressure fluctuations or low pressure at idle, Metal shavings visible in oil or filter, Check engine light with misfire codes in severe cases

Fix: This is the big one. The M113K supercharged engine is notorious for rod bearing and main bearing failures, often requiring complete engine teardown or replacement. Short block replacement takes 25-35 hours, full rebuild with machine work takes 35-50 hours. Many shops recommend replacing all bearings, ARP studs, oil pump, and valve stem seals while the engine is apart. Some owners opt for used or remanufactured engines to save time.

Estimated cost: $12,000-25,000

Typical onset: 70,000-110,000 mi

Symptoms: Oil in coolant (strawberry milkshake appearance in expansion tank), Transmission slipping or harsh shifts, Coolant in transmission fluid, Overheating transmission or engine

Fix: The transmission oil cooler inside the radiator fails and allows coolant and ATF to mix, contaminating both systems. Requires new radiator, complete transmission fluid flush (often multiple flushes), new transmission filter, coolant flush, and sometimes torque converter or full transmission rebuild if contamination was severe. The job itself is 6-10 hours but flushing protocol adds time.

Estimated cost: $2,500-8,000

Typical onset: 90,000-130,000 mi

Symptoms: High-pitched whine or squeal from supercharger area, Grinding noise during acceleration, Loss of boost pressure, Reduced power output

Fix: The Eaton M113K supercharger develops bearing wear or the coupler deteriorates. Supercharger must be removed (4-6 hours removal/reinstall) and either rebuilt with new bearings, seals, and coupler, or replaced with remanufactured unit. Many owners upgrade to ported units during this service.

Estimated cost: $2,000-4,500

Typical onset: 60,000-100,000 mi

Symptoms: Vehicle sagging on one corner, especially after sitting overnight, Airmatic warning light and suspension malfunction messages, Compressor running excessively or constantly, Harsh ride quality or uneven stance

Fix: Air struts develop leaks in the rubber bladders, and the air compressor wears out from overwork. Each strut replacement is 2-3 hours, compressor is 3-4 hours. Most mechanics recommend replacing struts in pairs (front or rear). Compressor relay can also fail. Some owners convert to coilovers to eliminate the system entirely.

Estimated cost: $1,800-4,000

Typical onset: 80,000-140,000 mi

Symptoms: Harsh or delayed shifts, especially 2-3 or 3-4, Transmission slipping in certain gears, Limp mode activation, Multiple transmission-related fault codes

Fix: The 5-speed 722.6 transmission develops conductor plate (wiring harness inside transmission) failures and valve body wear. Requires transmission pan removal, valve body removal and replacement or rebuild, new conductor plate, fluid and filter. This is a 8-12 hour job and should include complete 13-pin connector inspection.

Estimated cost: $2,200-4,000

Symptoms: Red brake warning light with message 'Brake Visit Workshop', Reduced braking power or complete brake failure, Loud humming or whining from brake system, Brake pedal feels abnormal or unresponsive

Fix: The SBC electrohydraulic brake system has a limited-life pump that Mercedes extended warranty coverage on, but many 2008s are now out of coverage. When it fails, braking ability is severely compromised. Requires complete SBC unit replacement (pump, accumulator, control unit assembly). This is 4-6 hours with proper bleeding and calibration with Star Diagnostics.

Estimated cost: $2,500-4,500

Typical onset: 70,000-120,000 mi

Symptoms: No-start condition or extended cranking, Rough idle or stalling, Check engine light with P0335 or P0340 codes, Intermittent cutting out while driving

Fix: These sensors fail from heat exposure and cause drivability issues or no-starts. Crank sensor is behind the starter and requires starter removal (3-4 hours total). Cam sensors are easier at 1-2 hours each. Always replace with OEM Mercedes or Bosch parts—aftermarket sensors frequently fail prematurely on this engine.

Estimated cost: $400-900