2010 MERCEDES-BENZ CLS55 AMG

Typical onset: 70,000-120,000 mi

Symptoms: metallic knocking at idle that increases with RPM, oil pressure drops or fluctuates, metal shavings in oil, sudden catastrophic failure with no warning in some cases

Fix: Rod bearings wear prematurely on M113K engines, especially those driven hard or with extended oil change intervals. Once knocking starts, engine disassembly is required. Many owners opt for full short block replacement or engine rebuild with upgraded bearings. Labor: 25-35 hours for proper rebuild.

Estimated cost: $8,000-15,000

Typical onset: 80,000-130,000 mi

Symptoms: whining or grinding noise from front of engine, supercharger oil leaking from nose cone, reduced boost pressure, check engine light with underboost codes

Fix: The Eaton M45 supercharger's input shaft bearing wears out, and the rubber coupler deteriorates. Requires supercharger removal and rebuild with new bearings, seals, and coupler. Labor: 8-12 hours.

Estimated cost: $2,500-4,000

Typical onset: 90,000-140,000 mi

Symptoms: harsh or delayed shifts, especially 2-3 and 3-4, limp mode activation, transmission slipping under load, multiple transmission fault codes

Fix: The 5G-Tronic transmission (722.6) develops issues with the valve body and conductor plate. Solenoids fail and wiring harness within the conductor plate cracks. Requires transmission pan removal, valve body R&R, and often a new conductor plate. Labor: 6-8 hours.

Estimated cost: $1,800-3,200

Typical onset: 60,000-100,000 mi

Symptoms: transmission fluid puddles under vehicle, burnt transmission fluid smell, low fluid level warnings, transmission overheating

Fix: Hard lines and rubber hoses running to the auxiliary transmission cooler crack and leak, often at connection points. Requires replacement of affected lines. Access can be tight. Labor: 2-4 hours depending on which lines fail.

Estimated cost: $400-900

Typical onset: 80,000-120,000 mi

Symptoms: vehicle sagging on one corner overnight, compressor running constantly, suspension warning light, harsh ride quality

Fix: Air struts develop leaks in the bladders, and the compressor wears out from constant cycling. Front struts fail more often than rears. Each strut replacement: 2-3 hours. Compressor replacement: 3-4 hours. Many owners convert to conventional coilovers to avoid recurring costs.

Estimated cost: $1,500-2,500 per strut; $1,800-2,800 for compressor

Symptoms: red brake warning light with message to visit workshop immediately, increased brake pedal effort, ABS and ESP lights illuminated, brake system entering emergency mechanical mode

Fix: The SBC system was recalled and extended warranty covered many, but some 2010 units still fail. When the hydraulic pump or accumulator fails, braking still works but loses power assist. Requires complete SBC unit replacement. Labor: 4-6 hours.

Estimated cost: $2,000-3,500