The 2009 CLK350 with the M272 V6 is a stylish coupe undermined by catastrophic engine weaknesses—balance shaft and timing chain issues that can grenade the motor if neglected. The transmission and cooling systems also demand attention, but the engine is the deal-breaker.
Symptoms: Rattling noise on cold start that disappears when warm, Check engine light with camshaft position codes, Sudden catastrophic engine failure with metal shavings in oil, Complete loss of power
Fix: The balance shaft sprocket gear wears and fragments, sending metal through the engine. Requires complete engine teardown or replacement. If caught early (just noise), balance shaft delete kit plus timing chain service runs 18-25 labor hours. After failure, you're looking at short block replacement or engine rebuild at 35-50 hours.
Estimated cost: $4,500-8,500 preventive; $8,000-15,000 after failure
M272 Timing Chain Stretch and Guide Failure
Common · high severity
Typical onset: 80,000-140,000 mi
Symptoms: Rattling on startup for first 3-5 seconds, Check engine light with timing correlation codes, Rough idle and misfires, Metal debris in oil filter
Fix: Timing chains stretch and guides wear through, risking jumped timing and valve-to-piston contact. Complete timing chain service includes all three chains, guides, tensioners, and cam adjusters. While you're in there, do balance shaft delete if not already done. 20-28 labor hours depending on additional damage assessment.
Estimated cost: $3,500-6,000
Transmission Valve Body and Conductor Plate Failure (722.6 5-speed)
Common · medium severity
Typical onset: 90,000-150,000 mi
Symptoms: Harsh or delayed 2-3 shift, Limp mode with transmission fault codes, Slipping between gears, No reverse or erratic shifting pattern
Fix: The 722.6 valve body and conductor plate (13-pin version) develops internal wear and electrical faults. Requires trans pan removal, valve body R&R, and new conductor plate with updated 13-pin connector. Fluid and filter service mandatory. 8-12 labor hours.
Estimated cost: $1,800-3,200
Crankcase Ventilation System Plugging
Common · medium severity
Typical onset: 60,000-100,000 mi
Symptoms: Oil consumption increase (1 qt per 1,000 mi), Oil in intake manifold and throttle body, Rough idle and hesitation, Whistling noise from engine bay
Fix: Oil separator valve in valve cover clogs, causing positive crankcase pressure that pushes oil past seals and rings. Requires valve cover removal and full CCV system replacement including separator, lines, and PCV valve. Often combined with intake manifold cleaning. 6-8 labor hours.
Estimated cost: $1,200-2,000
Transmission Oil Cooler Leaks
Occasional · medium severity
Typical onset: 80,000-130,000 mi
Symptoms: Transmission fluid dripping from front of car, Low transmission fluid warnings, Burnt smell after highway driving, Pink fluid spots on driveway
Fix: External transmission oil cooler develops leaks at crimped connections or through corrosion. Accessed from underneath, requires cooler replacement and complete fluid flush. If coolant enters transmission through internal leaks (less common), trans rebuild required. External cooler only: 3-4 labor hours.
Estimated cost: $600-1,200 external cooler only
Front Engine Mount (Transmission Mount) Failure
Occasional · low severity
Typical onset: 70,000-120,000 mi
Symptoms: Clunk when shifting from Park to Drive, Vibration at idle in gear, Excessive engine movement visible when revving, Transmission tunnel vibration
Fix: Hydraulic engine/transmission mounts collapse internally, allowing excessive powertrain movement. Front mount is most common failure point. Requires subframe access and careful alignment during installation. 3-5 labor hours depending on access.
Estimated cost: $800-1,400
Owner tips
Change oil every 5,000 miles MAX with quality 0W-40 synthetic—the M272 is unforgiving with extended intervals
Inspect timing chain condition with borescope at every oil change after 60k miles; catching rattles early saves the engine
Budget $5,000-8,000 for inevitable timing chain and balance shaft service before 100k miles—it's when, not if
Transmission fluid service every 40,000 miles with genuine MB fluid prevents valve body issues
Walk away from any CLK350 without complete service records proving timing chain work was done
Hard pass unless you find one under $8,000 with fresh timing chains and balance shaft delete already done—otherwise you're buying someone else's ticking time bomb.
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.
Fitment notes: Battery located in trunk on right side; AGM type required for this model
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Every control module on the 2006-2009 Mercedes-Benz CLK350 C209 — where it lives, replacement time, and what it takes to program a replacement. Modules marked dealer / factory tool won't work after a part swap alone — budget for programming.
COMAND Control Unit (COMAND)2.5 hr R&Rdealer / factory tool +0.5 hr▸ programming details
📍 Behind center dashboard, integrated with head unit
🔧 Star Diagnosis DAS/Xentry
⚠️ Optional equipment. Dashboard removal required. Navigation DVD region coding may be needed. MOST bus gateway function.
⚠️ Critical security component. Requires VIN coding, key programming, and synchronization with ECM and cluster. Steering lock motor often fails; replacement requires dealer authorization.
Electronic Stability Program / Anti-lock Brake System (ESP/ABS)1.5 hr R&Rdealer / factory tool +0.5 hr▸ programming details
📍 Engine bay, left front corner near brake master cylinder
Parktronic Control Unit (PTS)0.5 hr R&Raftermarket tool +0.2 hr▸ programming details
📍 Trunk, right side behind trim panel
🔧 Star Diagnosis or Autel
⚠️ Optional equipment. Sensor calibration may be needed after replacement.
Fuel Pump Control Module (FPCM)0.4 hr R&Rno coding
📍 Trunk floor, under trunk mat near fuel tank
⚠️ Simple relay/driver module. No coding typically required.
Aftermarket tool coverage varies by software version and vehicle build — treat "aftermarket tool" rows as "usually possible" and verify against your tool maker's coverage list before promising a customer. Spot a wrong location or hour? Tell us — corrections ship fast here.
Size-standard part numbers — verify your connector type before buying. Rear blades are model-specific; check the package's vehicle list.
Fuel economy figures are EPA data via fueleconomy.gov (median across matching trims). Performance figures are compiled estimates for the 2009 Mercedes-Benz CLK350 C209 3.5L V6 M272 and can vary by trim.
🔧 Database maintained under the daily editorial review of Chris Hackleman · Master Technician · 20+ years and Jeff Moore · Master Lexus & Toyota Mechanic · 20+ years.