Mercedes-Benz CLK C209
Weaknesses, engine ratings and buying advice
The CLK C209 (2002–2009) succeeds the C208 on the W203 platform — more refined, more modern, but with one critical weakness that defines the purchase: the Valeo radiator. Vehicles built before September 2003 have a combined radiator whose integrated transmission oil cooler fails internally — coolant enters the automatic gearbox and destroys the clutch packs. Transmission damage = often a write-off. Before every purchase: check coolant for milky discolouration, smell the transmission fluid (sweet = coolant contamination). Cars from 10/2003 onwards have the revised cooler — much safer.
The cabriolet (A209) has seven hydraulic cylinders in the roof mechanism — and every single one can leak. Main cylinder, tension bow cylinders, side panel cylinders — when one goes, the rest follow. Individual repair rarely pays off, full overhaul of all cylinders $5,500–22,000. Relays and micro-switches in the roof control wear out additionally. When buying a cabriolet: operate the top at least three times fully, check trunk for oil traces.
Engine choice: The M112 (CLK 240/320, until 2005) is the most carefree engine — proven robust, no serious weaknesses. The M272 (CLK 280/350, from 2005) has the notorious balance shaft sprocket: on engines before September 2006 (serial number below 468993) the insufficiently hardened idler gear wears and destroys the entire timing chain drive — engine removal mandatory, $2,800–6,000. Serial number check is essential. The 7G-Tronic (722.9, from 2005) is prone to valve body wear — harsh shifts, limp mode, $1,100–3,800. SAM module (signal processing) is susceptible to water damage.
Test-drive checklist: Coolant colour (milky = Valeo problem, pre-09/2003). Automatic: cycle gently through all gears, jerk at 2→3 = valve body. Check M272 serial number via VIN. Cabriolet: operate top fully open and closed, check trunk for oil. Underbody for sill rust (early models 2002–2004).
2026 market: CLK 200K/220 CDI Coupe from $5,500. CLK 320/350 Coupe $8,800–16,500. Cabriolet +30–50% premium. CLK 63 AMG $22,000–38,500. `Insider pick:` CLK 320 (M112) Coupe 2004–2005, after the Valeo radiator era, before M272 issues — the sweet spot. Predecessor is the CLK C208.
507 PS
CLK 63 AMG Black Series · Benzin
CLK 63 Black Series — DTM for the Road
Legendary!457–525 PS
6.2L V8 AMG Benzin
10 weaknesses
Stay Away!Body Variants
The Mercedes-Benz CLK C209 is available as Convertible and Coupé — choose your body type for specific insurance data:
Generations
Engine Overview
The Mercedes-Benz CLK C209 is available with 13 engine variants — from 120 to 525 hp. 1 variants had engine changes — the model year is crucial.
Widely used Mercedes diesel with aluminium block and steel liner. High mileages possible but known for injector seal issues, timing chain stretch and EGR problems.
- !! Chain Tensioner Seal Leaking — Recall
Over 100,000 vehicles recalled: the chain tensioner seal leaks, allowing engine oil to drip onto the exhaust system and potentially ignite.
Symptoms: Dropping oil level, oil smell from engine bay, oily deposits under the vehicle, possible oil fire - !! Timing Chain Stretch (Simplex Chain) from 150,000 km
The OM651 uses a simplex timing chain. With short-trip driving and overdue oil change intervals the chain stretches.
Symptoms: Light rattling noise on cold start from the rear of the engine, no fault code stored - !! Piezo Injector Faults from 80,000 km
Same Delphi piezo injector problems as in the DE18: 220 CDI and 250 CDI variants affected. Mercedes replaced them with solenoid injectors as part of a service action.
Symptoms: Vibrations and rough running especially under acceleration, elevated fuel consumption
+ 3 more engine weaknesses + vehicle weaknesses
Five-cylinder diesel with common rail. Unusual cylinder count, good balance of power and economy. Prone to blocked swirl flaps.
- !! "Black Death" -- injector seal failure with tar formation from 150,000 km
The most notorious problem in the OM612/OM646 CDI family: failing injector sealing rings allow combustion gases to escape. A black, tar-like mass forms around the injectors.
Symptoms: Black tar visible around injectors, hissing or knocking under load, diesel smell in interior - !! EGR cooler fails -- coolant in intake from 150,000 km
The EGR cooler on the OM612 can develop internal leaks and introduce coolant into the intake. This leads to white smoke, coolant loss and in the worst case hydro-lock.
Symptoms: White smoke from exhaust, coolant loss, sweet smell from exhaust, coolant in air filter housing - !! Cylinder head crack -- coolant loss under load from 200,000 km
Cylinder head cracks can form in the OM612 between two valves, only becoming visible under load.
Symptoms: Coolant loss without visible leak, white smoke, bubbling in coolant reservoir under load.
+ 3 more engine weaknesses + vehicle weaknesses
V6 diesel with common rail and piezo injectors. Powerful and refined. Known for blocked oil coolers, swirl flap failure and EGR problems. High mileages possible with good maintenance.
- !! Oil Cooler Gaskets Leaking — Oil and Coolant Loss from 120,000 km
The best-known problem of the OM642: the oil cooler gaskets in the V-section of the engine fail. Oil leaks into the coolant or externally. Particularly prone on vehicles built up to 2009.
Symptoms: Oil loss warning, oil spots under the left side of the vehicle, oil streaks visible on the belt tensioner - !! Swirl Flap Linkage Breaks — Plastic Joint Fails from 100,000 km
The plastic linkages of the swirl flaps in the OM642 intake manifold break. Aluminium repair kits are available and more durable. In the event of complete failure there is a risk of debris entering the engine.
Symptoms: Engine warning light, fault codes for intake flap/swirl flap, power loss particularly at low rpm - !! Injector Seal Leaking — Soot Deposits and Diesel in Oil from 120,000 km
Piezo injectors seal poorly from heat, diesel enters the engine oil. Oil loses lubrication properties, tar-like residue around injectors is the typical telltale sign.
Symptoms: Rough idle, increased fuel consumption, knocking noises, oil level rising due to diesel contamination, engine oil smells of diesel
+ 4 more engine weaknesses + vehicle weaknesses
Compact four-cylinder with mechanical supercharger. Known for timing chain stretch from approx. 100,000 km. Supercharger magnetic clutch can fail. Manual gearbox rare.
- !! Timing Chain Stretches Prematurely from 85,000 km
The simplex timing chain on the M271 is the most well-known wear issue: it can stretch before 100,000 km. In advanced stages it skips teeth and causes engine damage.
Symptoms: Rattling on cold start (diesel-like noise), camshaft fault codes, check engine light, in extreme cases engine damage - !! Camshaft Adjuster Leaks — Oil in Wiring Harness from 120,000 km
The camshaft adjuster solenoids develop leaks. The wiring harness absorbs oil by capillary action, which migrates as far as the engine ECU and damages it.
Symptoms: CEL with P0010/P0015, oil traces at camshaft connectors, in worst case ECU failure - !! Camshaft Adjuster Leaks Oil into Connector from 100,000 km
The camshaft adjuster seals on the M271 become porous and allow oil into the electrical connectors. The result is fault codes and check engine light.
Symptoms: Check engine light, camshaft adjuster fault codes, rough running, oil in adjuster connector
+ 3 more engine weaknesses + vehicle weaknesses
Compact four-cylinder with mechanical supercharger. Known for timing chain stretch from approx. 100,000 km. Supercharger magnetic clutch can fail. Manual gearbox rare.
- !! Timing Chain Stretches Prematurely from 85,000 km
The simplex timing chain on the M271 is the most well-known wear issue: it can stretch before 100,000 km. In advanced stages it skips teeth and causes engine damage.
Symptoms: Rattling on cold start (diesel-like noise), camshaft fault codes, check engine light, in extreme cases engine damage - !! Camshaft Adjuster Leaks — Oil in Wiring Harness from 120,000 km
The camshaft adjuster solenoids develop leaks. The wiring harness absorbs oil by capillary action, which migrates as far as the engine ECU and damages it.
Symptoms: CEL with P0010/P0015, oil traces at camshaft connectors, in worst case ECU failure - !! Camshaft Adjuster Leaks Oil into Connector from 100,000 km
The camshaft adjuster seals on the M271 become porous and allow oil into the electrical connectors. The result is fault codes and check engine light.
Symptoms: Check engine light, camshaft adjuster fault codes, rough running, oil in adjuster connector
+ 3 more engine weaknesses + vehicle weaknesses
Three-valve V6 with individual ignition coils. Smooth and strong. Typical weak points: crankcase breather and intake manifold flaps. High mileages achievable.
- !! Camshaft Adjuster Leaks Oil into Wiring Harness from 130,000 km
The camshaft adjuster solenoid on the M112 develops a leak and draws oil by capillary action into the wiring harness. Oil can migrate as far as the engine ECU and destroy it.
Symptoms: Cold-start rattling that disappears after 1–2 seconds, camshaft adjuster fault code, oil traces at wiring connector, later ECU faults - !! Intake Manifold Vacuum Hose Breaks from 120,000 km
The vacuum hose for the variable intake manifold on the M112 becomes brittle and breaks. The swirl flaps stick. The hose is not available individually — the entire intake manifold is needed.
Symptoms: Power drop, slight hesitation at part throttle, engine runs but without full power - !! Valve Cover Gasket and Front Cover Gasket Leaking from 130,000 km
On the M112 V6 the valve cover gaskets become porous over time. Especially the rubber seals on the front cover between the timing cover and engine block fail on virtually all high-mileage M112 engines.
Symptoms: Oil spots on the floor, oil smell after driving, oily engine bay, dropping oil level
+ 4 more engine weaknesses + vehicle weaknesses
Four-valve V6 with variable valve timing. Smooth and powerful. Known for balance shaft wear (revision sprocket) on early build years. Balance shaft gear problem addressed by Mercedes with a recall.
- !! Balance Shaft Sprocket Wears Prematurely from 140,000 km
The plastic balance shaft sprocket on the M272 wears prematurely from the timing chain. The right cylinder bank goes out of timing. Affected up to end of October 2006.
Symptoms: Fault codes P0016/P0017 (camshaft right bank), chain rattling, rough running at idle, in extreme cases engine damage - !! Timing Chain Stretches and Damages Timing from 120,000 km
Alongside the balance shaft issue the M272 shows premature timing chain stretch. Chain wear on softer sprockets leads to timing deviations.
Symptoms: Chain noise especially on cold start, camshaft fault codes, rough running, engine irregularities - !! Camshaft Adjuster Leaks — Wiring Harness Contaminated from 90,000 km
Four camshaft adjuster solenoids (two per cylinder bank) develop leaks; oil creeps into the wiring harness as far as the ECU. Repair costs up to €1,700 documented.
Symptoms: CEL, oil traces at camshaft connectors, lambda sensor failure due to oil contamination, non-specific faults that recur
+ 3 more engine weaknesses + vehicle weaknesses
Three-valve V6 with individual ignition coils. Smooth and strong. Typical weak points: crankcase breather and intake manifold flaps. High mileages achievable.
- !! Camshaft Adjuster Leaks Oil into Wiring Harness from 130,000 km
The camshaft adjuster solenoid on the M112 develops a leak and draws oil by capillary action into the wiring harness. Oil can migrate as far as the engine ECU and destroy it.
Symptoms: Cold-start rattling that disappears after 1–2 seconds, camshaft adjuster fault code, oil traces at wiring connector, later ECU faults - !! Intake Manifold Vacuum Hose Breaks from 120,000 km
The vacuum hose for the variable intake manifold on the M112 becomes brittle and breaks. The swirl flaps stick. The hose is not available individually — the entire intake manifold is needed.
Symptoms: Power drop, slight hesitation at part throttle, engine runs but without full power - !! Valve Cover Gasket and Front Cover Gasket Leaking from 130,000 km
On the M112 V6 the valve cover gaskets become porous over time. Especially the rubber seals on the front cover between the timing cover and engine block fail on virtually all high-mileage M112 engines.
Symptoms: Oil spots on the floor, oil smell after driving, oily engine bay, dropping oil level
+ 4 more engine weaknesses + vehicle weaknesses
Four-valve V6 with variable valve timing. Smooth and powerful. Known for balance shaft wear (revision sprocket) on early build years. Balance shaft gear problem addressed by Mercedes with a recall.
- !! Balance Shaft Sprocket Wears Prematurely from 140,000 km
The plastic balance shaft sprocket on the M272 wears prematurely from the timing chain. The right cylinder bank goes out of timing. Affected up to end of October 2006.
Symptoms: Fault codes P0016/P0017 (camshaft right bank), chain rattling, rough running at idle, in extreme cases engine damage - !! Timing Chain Stretches and Damages Timing from 120,000 km
Alongside the balance shaft issue the M272 shows premature timing chain stretch. Chain wear on softer sprockets leads to timing deviations.
Symptoms: Chain noise especially on cold start, camshaft fault codes, rough running, engine irregularities - !! Camshaft Adjuster Leaks — Wiring Harness Contaminated from 90,000 km
Four camshaft adjuster solenoids (two per cylinder bank) develop leaks; oil creeps into the wiring harness as far as the ECU. Repair costs up to €1,700 documented.
Symptoms: CEL, oil traces at camshaft connectors, lambda sensor failure due to oil contamination, non-specific faults that recur
+ 3 more engine weaknesses + vehicle weaknesses
Naturally aspirated V8 in three displacements from 4.3 to 5.5 litres — old-school character with no turbo lag. Linear power delivery, deep rumble from 2,000 rpm building to a hoarse roar above 5,000. Peak torque at 3,000; beyond that it thins out — yet it's silky in part-throttle and surprisingly economical. Achilles heel is the seals: rear crankshaft oil seal practically universal above 150,000 km (gearbox removal required, 600–900 EUR), valve covers and oil filter housing seep with age. All cheap parts. The one critical point: the rubber damper on the crankshaft pulley hardens with age — when it fails the pulley machines into the sump. Replace preventively every 150,000 km. Oil changes every 10,000 km with 5W-40, 16 spark plugs every 60,000–80,000 km — then 400,000 km is realistic.
- !! Vibration Damper/Pulley — Rubber Hardens from 170,000 km
The rubber damper in the crankshaft pulley hardens with age and can eat into the sump — catastrophic consequential damage. Preventive replacement every 150,000 km strongly recommended.
Symptoms: Unusual vibrations at idle, in worst case metallic scraping from below. Often no prior warning — sudden failure. - !! Rear Crankshaft Seal Leaking from 150,000 km
The rear crankshaft seal is leaking on virtually all M113 engines above 150,000 km. Gearbox removal required — 600–900 EUR workshop costs. If oil creeps into the torque converter it becomes expensive.
Symptoms: Oil drops or oil film visible at the engine-gearbox interface, oil loss without any other apparent leak on the engine. - !! Engine Mounts Worn Prematurely from 90,000 km
Engine mounts can fail before 100,000 km. Practical test: finger between the stabiliser bar and front sump — no clearance means the mount is dead. Not visually checkable without removal.
Symptoms: Vibrations in interior especially at idle, dull rumbling on acceleration, in worst case contact between engine and bodywork.
+ 7 more engine weaknesses + vehicle weaknesses
Large-displacement naturally aspirated V8, second generation with variable valve timing on all four camshafts. Technically related to the M272 V6 — shares its known balance shaft sprocket problem on build years before 2007 (engine number below 088611). From that number the sprocket was made of hardened steel. Check early engines for fault codes P0016/P0017 and cold-start chain noise. The 5.5-litre with 285 kW is the typical variant; the 5.0-litre with 225–250 kW is somewhat more forgiving in heavier vehicles. The M278 BiTurbo successor is more efficient and more powerful, but sounds considerably less characterful — the M273 is the last true naturally aspirated V8 from Stuttgart. Pre-purchase: always check for camshaft adjuster leaks (oil in wiring harness) and thermostat fault P0128. Oil changes every 10,000 km with MB 229.5.
- !! Balance shaft sprocket — same weakness as M272 from 140,000 km
The M273 V8 shares the balance shaft sprocket issue with the M272 V6. The soft composite material of the sprocket wears down, causing timing chain rattle.
Symptoms: Fault codes P0016/P0017, chain rattling, rough idle, power loss - !! Camshaft Adjuster Leaking — Oil in Wiring Harness from 110,000 km
As with the similarly-designed M272, the solenoid valves leak. The V8 has 4 per bank — consequential costs are particularly high due to more solenoids. Oil migrates by capillary action all the way to the ECU.
Symptoms: Check engine light with camshaft fault codes P0014/P0015/P0021/P0025, lambda sensor failures, in extreme cases ECU failure - !! Valve cover gaskets leaking on both sides from 130,000 km
Like the M113, the valve cover gaskets on the M273 V8 become porous over time. With a V8 having two cylinder heads, the workload doubles.
Symptoms: Oil spots under the vehicle, oil smell after hard driving, oily engine bay
+ 6 more engine weaknesses + vehicle weaknesses
Naturally aspirated V8 in three displacements from 4.3 to 5.5 litres — old-school character with no turbo lag. Linear power delivery, deep rumble from 2,000 rpm building to a hoarse roar above 5,000. Peak torque at 3,000; beyond that it thins out — yet it's silky in part-throttle and surprisingly economical. Achilles heel is the seals: rear crankshaft oil seal practically universal above 150,000 km (gearbox removal required, 600–900 EUR), valve covers and oil filter housing seep with age. All cheap parts. The one critical point: the rubber damper on the crankshaft pulley hardens with age — when it fails the pulley machines into the sump. Replace preventively every 150,000 km. Oil changes every 10,000 km with 5W-40, 16 spark plugs every 60,000–80,000 km — then 400,000 km is realistic.
- !! Vibration Damper/Pulley — Rubber Hardens from 170,000 km
The rubber damper in the crankshaft pulley hardens with age and can eat into the sump — catastrophic consequential damage. Preventive replacement every 150,000 km strongly recommended.
Symptoms: Unusual vibrations at idle, in worst case metallic scraping from below. Often no prior warning — sudden failure. - !! Rear Crankshaft Seal Leaking from 150,000 km
The rear crankshaft seal is leaking on virtually all M113 engines above 150,000 km. Gearbox removal required — 600–900 EUR workshop costs. If oil creeps into the torque converter it becomes expensive.
Symptoms: Oil drops or oil film visible at the engine-gearbox interface, oil loss without any other apparent leak on the engine. - !! Engine Mounts Worn Prematurely from 90,000 km
Engine mounts can fail before 100,000 km. Practical test: finger between the stabiliser bar and front sump — no clearance means the mount is dead. Not visually checkable without removal.
Symptoms: Vibrations in interior especially at idle, dull rumbling on acceleration, in worst case contact between engine and bodywork.
+ 7 more engine weaknesses + vehicle weaknesses
6.2-litre naturally aspirated V8, hand-built in Affalterbach to the 'One Man, One Engine' principle. 457–525 hp without any forced induction, rev limit at 7,200 rpm. The sound defines an era: a deep, bass-heavy rumble at 3,000 rpm, a scream above 5,000 that recalls American V8 racing engines. Throttle response is immediate — no turbo lag, no hesitation, every throttle command is executed instantly. Critical issue number one: camshafts wear out through inadequate cold-start lubrication with the factory 0W-40 oil. Switch to Ravenol 5W-40 RCS, let the engine idle for 10 seconds after a cold start, stay below 3,000 rpm until fully warm. Head bolt corrosion on engine numbers below 060658 (up to approx. 2010) — check without fail. Star Technical Bulletin 05.20/20b documents the tappet problem officially. Parts availability is becoming increasingly difficult — hydraulic tappets A1560500225 sometimes not available for months. Maintain the M156 properly and you have one of the most emotional V8s of the last 30 years.
- !! Head Bolt Corrosion — Coolant in Combustion Chamber from 50,000 km
All M156 up to engine number 060658 affected: head bolts corrode through coolant contact at the bolt head, in worst case break off. Coolant enters the combustion chamber — engine damage. Mercedes fitted improved bolts from approx. 2010 (20x A1560160769 + 4x N000000005754, approx. 108 EUR net). Preventive replacement strongly recommended.
Symptoms: Coolant loss without visible leak, white smoke from exhaust, oil-coolant mixture, check engine light, misfires on individual cylinders. - !! Camshaft Wear — Cold-Start Lubrication Deficit from 60,000 km
Main problem of the M156: the factory 0W-40 oil drains from the camshafts at standstill; at cold start the lobes run briefly dry. Wear deteriorates exponentially. Camshaft regrinding (TechnoCam and others) as a cheaper alternative to new parts — 50% saving. Always replace the 32 hydraulic tappets (INA A1560500225) at the same time.
Symptoms: Metallic ticking on cold start that disappears after 30–60 seconds, rough idle, power loss in the upper rev range. Remove valve cover and check lobe tips for wear. - !! Camshaft Adjuster — Locking Plate Wears Out from 70,000 km
The fit of the locking plate in the camshaft adjuster widens over time — the adjuster slips, timing shifts. Clattering on cold start is the first symptom. Reinforced locking plates (300–1,000 EUR for 4 pieces) as a permanent solution. Bearing cap torque 10 Nm, adjuster 45 Nm + 90°.
Symptoms: Rattling/clattering on cold start for 2–10 seconds, disappears after oil pressure build-up. With advanced wear: also audible when warm, rough idle, shifted timing, power loss.
+ 7 more engine weaknesses + vehicle weaknesses
6.2-litre naturally aspirated V8, hand-built in Affalterbach to the 'One Man, One Engine' principle. 457–525 hp without any forced induction, rev limit at 7,200 rpm. The sound defines an era: a deep, bass-heavy rumble at 3,000 rpm, a scream above 5,000 that recalls American V8 racing engines. Throttle response is immediate — no turbo lag, no hesitation, every throttle command is executed instantly. Critical issue number one: camshafts wear out through inadequate cold-start lubrication with the factory 0W-40 oil. Switch to Ravenol 5W-40 RCS, let the engine idle for 10 seconds after a cold start, stay below 3,000 rpm until fully warm. Head bolt corrosion on engine numbers below 060658 (up to approx. 2010) — check without fail. Star Technical Bulletin 05.20/20b documents the tappet problem officially. Parts availability is becoming increasingly difficult — hydraulic tappets A1560500225 sometimes not available for months. Maintain the M156 properly and you have one of the most emotional V8s of the last 30 years.
- !! Head Bolt Corrosion — Coolant in Combustion Chamber from 50,000 km
All M156 up to engine number 060658 affected: head bolts corrode through coolant contact at the bolt head, in worst case break off. Coolant enters the combustion chamber — engine damage. Mercedes fitted improved bolts from approx. 2010 (20x A1560160769 + 4x N000000005754, approx. 108 EUR net). Preventive replacement strongly recommended.
Symptoms: Coolant loss without visible leak, white smoke from exhaust, oil-coolant mixture, check engine light, misfires on individual cylinders. - !! Camshaft Wear — Cold-Start Lubrication Deficit from 60,000 km
Main problem of the M156: the factory 0W-40 oil drains from the camshafts at standstill; at cold start the lobes run briefly dry. Wear deteriorates exponentially. Camshaft regrinding (TechnoCam and others) as a cheaper alternative to new parts — 50% saving. Always replace the 32 hydraulic tappets (INA A1560500225) at the same time.
Symptoms: Metallic ticking on cold start that disappears after 30–60 seconds, rough idle, power loss in the upper rev range. Remove valve cover and check lobe tips for wear. - !! Camshaft Adjuster — Locking Plate Wears Out from 70,000 km
The fit of the locking plate in the camshaft adjuster widens over time — the adjuster slips, timing shifts. Clattering on cold start is the first symptom. Reinforced locking plates (300–1,000 EUR for 4 pieces) as a permanent solution. Bearing cap torque 10 Nm, adjuster 45 Nm + 90°.
Symptoms: Rattling/clattering on cold start for 2–10 seconds, disappears after oil pressure build-up. With advanced wear: also audible when warm, rough idle, shifted timing, power loss.
+ 7 more engine weaknesses + vehicle weaknesses
Vehicle Weaknesses
| Weakness | Cost | |
|---|---|---|
| 5G-Tronic: Coolant Ingress via Valeo Cooler Valeo transmission oil heat exchanger on pre-facelift models up to 09/2003 develops leaks. Coolant enters the transmission and destroys the clutch packs. Symptom: humming and juddering at low revs. Symptoms: Humming and juddering under light acceleration at low rpm, cloudy transmission fluid from 70,000 km | High | |
| 7G-Tronic Valve Body Worn 7G-Tronic (722.9) on later CLK models from 2005 suffers from worn valve body (conductor plate). Shifts become harsh, transmission enters limp mode. Oil changes every 60,000 km significantly extend service life. Symptoms: Harsh shifts between gears, delayed engagement of D or R, transmission limp mode from 100,000 km | High |
Test Reports
TÜV Report 2024
The CLK C209 sits at the age-appropriate average at the MOT inspection with typical wear characteristics.
2023-11Alternatives
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Known Problems and Issues +
A total of 86 weaknesses have been documented for the Mercedes-Benz CLK C209 (2002–2010) — 73 engine-related and 13 vehicle-related. 7 problem engines: OM651DE22 (2.1L Diesel), M271 (1.8L Kompressor), M272 (3.0-3.5L V6), M273 (5.0-5.5L V8), OM612 (2.7L 5-Zyl Diesel), OM642 (3.0L V6 Diesel), M156 (6.2L V8 AMG). Typical issues affect Gearbox, Electronics, Body, Brakes.
CLK (OM612, 2002–2005) — Stay Away!: "Black Death" -- injector seal failure with tar formation, EGR cooler fails -- coolant in intake, Cylinder head crack -- coolant loss under load. Power: 163–170 PS.
CLK (OM651DE22, 2005–2010) — Stay Away!: Chain Tensioner Seal Leaking — Recall, Timing Chain Stretch (Simplex Chain), Piezo Injector Faults. Power: 150 PS.
CLK (OM642, 2005–2010) — Stay Away!: Oil Cooler Gaskets Leaking — Oil and Coolant Loss, Swirl Flap Linkage Breaks — Plastic Joint Fails, Injector Seal Leaking — Soot Deposits and Diesel in Oil. Power: 224 PS.
CLK (M111, 1998–2003) — Be Careful: Head Gasket Ages and Leaks, Supercharger Magnetic Clutch Fails, Ignition Coils Wear Out Due to Neglected Spark Plugs. Power: 136 PS.
CLK (M112, 1998–2003) — Be Careful: Camshaft Adjuster Leaks Oil into Wiring Harness, Intake Manifold Vacuum Hose Breaks, Valve Cover Gasket and Front Cover Gasket Leaking. Power: 218 PS.
CLK (M113, 1999–2003) — Be Careful: Vibration Damper/Pulley — Rubber Hardens, Rear Crankshaft Seal Leaking, Engine Mounts Worn Prematurely. Power: 279 PS.
CLK (M111, 2000–2003) — Be Careful: Head Gasket Ages and Leaks, Supercharger Magnetic Clutch Fails, Ignition Coils Wear Out Due to Neglected Spark Plugs. Power: 163 PS.
CLK (M111, 2000–2003) — Be Careful: Head Gasket Ages and Leaks, Supercharger Magnetic Clutch Fails, Ignition Coils Wear Out Due to Neglected Spark Plugs. Power: 193–197 PS.
CLK (M112, 2002–2005) — Be Careful: Camshaft Adjuster Leaks Oil into Wiring Harness, Intake Manifold Vacuum Hose Breaks, Valve Cover Gasket and Front Cover Gasket Leaking. Power: 163–170 PS.
CLK (M113, 2002–2006) — Be Careful: Vibration Damper/Pulley — Rubber Hardens, Rear Crankshaft Seal Leaking, Engine Mounts Worn Prematurely. Power: 306 PS.
CLK (M113, 2002–2006) — Be Careful: Vibration Damper/Pulley — Rubber Hardens, Rear Crankshaft Seal Leaking, Engine Mounts Worn Prematurely. Power: 367 PS.
CLK (M271, 2002–2006) — Stay Away!: Timing Chain Stretches Prematurely, Camshaft Adjuster Leaks — Oil in Wiring Harness, Camshaft Adjuster Leaks Oil into Connector. Power: 163–170 PS.
CLK (M272, 2005–2010) — Stay Away!: Balance Shaft Sprocket Wears Prematurely, Timing Chain Stretches and Damages Timing, Camshaft Adjuster Leaks — Wiring Harness Contaminated. Power: 231 PS.
CLK (M272, 2005–2010) — Stay Away!: Balance Shaft Sprocket Wears Prematurely, Timing Chain Stretches and Damages Timing, Camshaft Adjuster Leaks — Wiring Harness Contaminated. Power: 272 PS.
CLK (M271, 2006–2010) — Stay Away!: Timing Chain Stretches Prematurely, Camshaft Adjuster Leaks — Oil in Wiring Harness, Camshaft Adjuster Leaks Oil into Connector. Power: 184 PS.
CLK (M273, 2006–2010) — Stay Away!: Balance shaft sprocket — same weakness as M272, Camshaft Adjuster Leaking — Oil in Wiring Harness, Valve cover gaskets leaking on both sides. Power: 387 PS.
CLK (M156, 2006–2010) — Stay Away!: Head Bolt Corrosion — Coolant in Combustion Chamber, Camshaft Wear — Cold-Start Lubrication Deficit, Camshaft Adjuster — Locking Plate Wears Out. Power: 481 PS.
CLK (M156, 2007–2009) — Stay Away!: Head Bolt Corrosion — Coolant in Combustion Chamber, Camshaft Wear — Cold-Start Lubrication Deficit, Camshaft Adjuster — Locking Plate Wears Out. Power: 507 PS.
What to watch out for with the Mercedes-Benz CLK? See the detailed listing of all engine and vehicle weaknesses in the sections above.
Frequently Asked Questions
What problems and weaknesses does the Mercedes-Benz CLK C209 have? +
What should I look for when buying a used Mercedes-Benz CLK C209? +
Which engine is recommended? +
Which Mercedes-Benz CLK C209 engine is the most fun? +
Is the Mercedes-Benz CLK C209 worth buying used? +
What horsepower variants are available for the Mercedes-Benz CLK C209? +
Last updated: February 2026 · All information without guarantee