2009 MERCEDES-BENZ SL

Typical onset: 40,000-90,000 mi

Symptoms: Excessive oil consumption (1 quart per 500-1000 miles), Blue smoke from exhaust on startup or acceleration, Loss of compression in one or multiple cylinders, Check engine light with misfire codes (P0300-P0308), Rattling or knocking noise from engine block

Fix: The M273 engine suffers from inadequate cylinder wall hardening that allows pistons and rings to score the bores. Once oil consumption begins, it escalates rapidly. Requires complete engine rebuild with re-sleeved or replaced block, all new pistons, rings, bearings. 35-50 labor hours for removal, rebuild, and reinstallation. Some owners opt for used engine replacement (25-30 hours) but risk inheriting same defect.

Estimated cost: $12,000-22,000

Typical onset: 60,000-120,000 mi

Symptoms: Loud grinding or metallic rattling from front of engine, Check engine light with cam/crank correlation codes, Metal shavings in oil during changes, Loss of oil pressure, Sudden catastrophic engine failure if gear teeth strip

Fix: The M273 balance shaft drive gears are undertorqued from factory and can strip teeth or seize. Requires front engine teardown to access timing components, replace balance shaft gears, chains, and guides. Often discovered during engine rebuild for scoring issues. Preventive replacement recommended at 60k-80k miles. 18-25 labor hours if caught early; if gears fail completely, metal debris contaminates entire engine requiring full rebuild.

Estimated cost: $4,500-8,000

Typical onset: 70,000-110,000 mi

Symptoms: White smoke from exhaust indicating coolant burning, Overheating or fluctuating temperature gauge, Coolant loss with no visible leaks, Milky oil on dipstick or oil cap, Rough idle and misfires

Fix: The M273 is prone to head gasket failure, particularly on bank 2 (passenger side). Requires removal of both cylinder heads, decking surfaces, new gaskets and head bolts. Given labor involved, most techs recommend addressing valve stem seals and inspecting for bore scoring simultaneously. 22-28 labor hours for both banks.

Estimated cost: $5,500-8,500

Typical onset: 60,000-100,000 mi

Symptoms: Transmission fluid spots under vehicle, Low transmission fluid warnings on dash, Harsh or delayed shifting, Burnt transmission fluid smell, Transmission slipping or limp mode if fluid critically low

Fix: The external transmission oil cooler lines and cooler itself develop leaks due to corrosion and vibration wear. Lines run along frame rails and are exposed to road salt. Replace cooler assembly and both hard lines. If caught early before fluid runs critically low, transmission avoids damage. 4-6 labor hours.

Estimated cost: $1,200-2,200

Typical onset: 50,000-90,000 mi

Symptoms: Clunking when shifting from Park to Drive or Reverse, Vibration through floorboard at idle, Excessive drivetrain movement visible under throttle, Knocking sound over bumps from transmission tunnel area

Fix: The rubber transmission mounts deteriorate and collapse, allowing excessive drivetrain movement. This is exacerbated by the heavy V8 and aggressive shifting of the seven-speed. Replace all transmission mounts (typically 2-3 depending on configuration). Requires supporting transmission and drivetrain. 3-4 labor hours.

Estimated cost: $800-1,400

Typical onset: 80,000-120,000 mi

Symptoms: Rough running or hesitation under load, Difficulty starting after sitting, Check engine light with fuel trim codes, Loss of power at highway speeds, Stalling or stumbling during acceleration

Fix: The in-tank fuel filter and pre-pump filter screen become clogged with debris from tank corrosion or contaminated fuel. Requires fuel tank removal to access pump assembly and filters. Many techs recommend replacing entire fuel pump module given labor involved. Tank inspection for rust/debris essential. 5-7 labor hours.

Estimated cost: $1,200-2,000

Typical onset: 60,000-100,000 mi

Symptoms: ABC warning light on dash, Vehicle sagging on one corner when parked, Harsh ride quality or bottoming out, Hydraulic fluid leaks under vehicle (green fluid), Inability to raise/lower suspension

Fix: Active Body Control (ABC) system uses hydraulic struts and valve blocks that develop leaks or failures. Front struts most common ($2,500-3,500 each side), valve block failures ($3,000-5,000), or pump issues ($2,000-3,500). Diagnosis requires Mercedes STAR system. Each strut is 3-4 hours, valve block 6-8 hours, pump 4-5 hours. System requires specialized bleeding procedure.

Estimated cost: $2,500-6,000