2007 MERCEDES-BENZ CLS55 AMG

Typical onset: 70,000-130,000 mi

Symptoms: Excessive oil consumption (1+ quart per 500-1000 miles), Blue smoke on cold start or acceleration, Loss of compression leading to misfires, Metal debris in oil, Complete engine seizure in worst cases

Fix: M113K engines suffer from inadequate piston ring tension and poor cylinder wall treatment. Pistons rock in bores, glazing cylinders and causing ring flutter. Requires complete engine rebuild with block resurfacing or liner installation, upgraded piston rings, new pistons. Many opt for full short block replacement. 35-50 labor hours depending on approach.

Estimated cost: $12,000-22,000

Typical onset: 80,000-150,000 mi

Symptoms: Sudden metallic rattling or knocking from deep in engine, Metal shavings in oil, Check engine light with cam/crank correlation codes, Catastrophic engine damage if gear teeth shear

Fix: The balance shaft drive gears on M113K can strip teeth or fail, sending metal through the entire engine. Requires complete engine disassembly, replacement of balance shaft assembly, timing components, and inspection of all oil galleries for debris. Often discovered during rebuild for other issues. 40-55 hours if caught early, totaled engine if teeth circulate.

Estimated cost: $8,000-15,000

Typical onset: 60,000-120,000 mi

Symptoms: Transmission fluid puddles under vehicle, Burnt transmission fluid smell, Slipping or harsh shifts from low fluid, Red/brown fluid visible on cooler lines at radiator

Fix: The 722.6 transmission cooler lines and connections at the radiator corrode and leak. Lines run along frame rails and are exposed to road salt. Requires replacement of metal lines and/or rubber hoses, plus fluid flush. 3-5 hours labor depending on which sections fail.

Estimated cost: $800-1,500

Typical onset: 70,000-110,000 mi

Symptoms: Clunk when shifting from Park to Drive or Reverse, Vibration at idle in gear, Excessive driveline movement felt through chassis, Visible separation or tearing of rubber mount

Fix: The large transmission mount deteriorates from the stress of 510 lb-ft torque and supercharger heat. Rubber separates from metal backing. Replacement requires supporting transmission and removing bolts from crossmember. 2-3 hours labor.

Estimated cost: $400-700

Typical onset: 90,000-140,000 mi

Symptoms: Whining or grinding noise from front of engine, Supercharger squeal that changes with RPM, Loss of boost pressure, Metal shavings in supercharger oil

Fix: The Eaton M113 supercharger input shaft bearing and rubber coupler wear out. Bearing failure sends metal into the blower. Requires removal of supercharger, replacement of snout bearings, coupler, and often full supercharger rebuild or replacement. 8-12 hours labor.

Estimated cost: $2,500-4,500

Typical onset: 80,000-130,000 mi

Symptoms: Vehicle sits low on one or more corners, Airmatic warning on dash, Compressor runs excessively, Visible oil residue on strut bodies

Fix: Airmatic air struts develop leaks in the rubber bladder or seals. Front struts more common than rear. Requires strut replacement (no rebuild option from MB). Compressor often also worn from overwork. 4-6 hours for pair of fronts or rears.

Estimated cost: $2,000-3,500

Typical onset: 90,000-150,000 mi

Symptoms: No-start or crank/no-start condition, Fuel gauge reading erratically or stuck, Stumbling or hesitation under hard acceleration, Whining noise from fuel tank area

Fix: Fuel pump assemblies fail from age and ethanol fuel degradation. The CLS has a large saddle tank requiring access through rear seat area. Requires dropping tank or accessing through service panel, replacing entire pump/sender assembly. 4-5 hours labor.

Estimated cost: $1,200-2,000