Mercedes CLK A209 Engines — The Complete UK Guide
Every engine fitted to the CLK A209 cabriolet — from the M271 Kompressor four-cylinders to the M112 and M272 V6 petrols, the M113 and M156 V8s, and the OM646, OM612 and OM642 diesels. Real UK replacement costs, honest failure data, and the balance-shaft and swirl-flap issues that define this generation's ownership story. Backed by 252+ real UK CLK enquiries in 2025 [MB-VERIFIED].
Explore A209 Engines
Mercedes CLK A209 Engine Codes — The Complete Database
Every engine fitted to the CLK A209 cabriolet specifically — from the entry-level four-cylinder Kompressor to the fire-breathing M156 V8 in the CLK 63 AMG.
Overview
Mercedes CLK A209 — Overview
The A209 is the convertible body style of the second-generation CLK-Class, launched in February 2002 as the successor to the A208 cabriolet .
Based on the Mercedes W203 C-Class platform, it uses rack-and-pinion steering instead of the recirculating-ball design of the previous generation . The engine range evolved significantly: early cars offered M112 V6 petrols, M113 V8s, and OM612 five-cylinder diesels . A 2005 facelift brought revised styling, the M272 and M273 V6/V8 petrols, and the OM646 and OM642 diesels . The range-topping CLK 63 AMG, introduced in 2006, used the M156 6.2-litre V8 producing 474bhp . The A209 was the last complete car built by Karmann before the facility closed .
Key Facts
Platform
Mercedes W203 (shared with C-Class)
Predecessor
A208
Successor
A207 E-Class Cabriolet
Sibling body style in this generation
C209 Coupé
Market Intelligence
The CLK A209 generated 252 real UK engine enquiries in 2025 [MB-VERIFIED], concentrated on the M112/M272 V6 petrols and OM646 diesel as these cars enter enthusiast-owner territory.
Best & Worst Engines
Best Diesel Overall
OM646.963 (CLK 220 CDI, 2005–2009)
“The 2.1-litre OM646 is the most refined and reliable diesel in the A209 range. It replaced the less-reliable OM612 five-cylinder and offers 148bhp with a genuine 200,000-mile-plus lifespan when properly maintained . Injector seal 'Black Death' is the only real concern — and it's easily preventable.”
Who it's for: buyers who want diesel economy without the OM612's five-cylinder quirks.
Best Petrol Overall
M112.953 (CLK 320, 3.2-litre V6)
“The 3.2-litre M112 V6 is arguably the most bulletproof engine ever fitted to a CLK. 218bhp of smooth, naturally aspirated power, no balance-shaft issues, no timing-chain worries — just a robust, proven V6 that keeps going. The 2.6-litre M112.912 in the CLK 240 is equally solid .”
Who it's for: buyers who want V6 smoothness without the M272's balance-shaft risk.
Highest Risk
M271.940/M271.955 (CLK 200 Kompressor)
“The 1.8-litre supercharged M271 is the A209's entry-level petrol — but it comes with known issues: timing chain stretch, camshaft adjuster wear, and supercharger clutch failure . Repair costs can quickly exceed the value of a budget CLK. If you buy one, ensure the chain and tensioner have been replaced.”
Who it's for: budget-conscious buyers willing to accept higher maintenance costs.
Most Expensive Failure
M156.982 (CLK 63 AMG)
“The 6.2-litre M156 V8 is a masterpiece — 474bhp of naturally aspirated AMG thunder. But when it fails, it fails expensively. Camshaft adjusters, lifters, and the sheer cost of AMG-specific parts mean replacement bills frequently hit five figures. The Black Series M156.983 is even more costly.”
Who it's for: collectors and enthusiasts with deep pockets.
Best Value
M112.912 (CLK 240, 2.6-litre V6)
“Often overlooked in favour of the more powerful CLK 320, the 2.6-litre M112 offers 170bhp, the same bulletproof reliability, and significantly better fuel economy. It's cheaper to buy, cheaper to insure, and cheaper to run — the sweet spot in the A209 petrol range.”
Who it's for: buyers who want V6 refinement without the running costs of a larger engine.
Most Overlooked
OM642.920 (CLK 320 CDI, 3.0-litre V6 diesel)
“The 3.0-litre OM642 V6 diesel is rare in the A209 but offers 224bhp and 510Nm of torque — more than the CLK 500 V8 in pulling power . It's a refined, powerful diesel that transforms the CLK into a genuine grand tourer. The OM642 is well-regarded for reliability, though early units can have oil cooler seal issues.”
Who it's for: buyers who want diesel torque without the four-cylinder's limitations.
Mercedes CLK A209 — Ownership Economics
The A209 rule
A £2,500–£4,500 OM646 recon against a £5,000 A209 sits at 50–90% of the car's value. On a sub-£4,000 CLK, that brushes our 70% Mercedes threshold — we'll honestly tell you to walk away. Against a well-kept £8,000+ example (particularly a V8 or AMG), the same recon drops to a routine 31–56% — a repair decision, not a financial one. Value the car first. For the M156 AMG, the maths is different — if you can afford a £15,000+ CLK 63, you can afford the maintenance.
Common Problems
A209 Engine Replacement Costs — By Engine and Condition
No Generation variance from the Model Page's baseline figures — A209 cabriolet shares its W203-derived engine bay with the C209 coupé, so costs are inherited directly per the Authority Model, with no divergence note required. M156 AMG costs reflect AMG-specific parts and specialist labour requirements.
Core Variants
Core Variants
Diesel Variants
Scope note: All variants listed are A209 cabriolet only. C209 Coupé shares most of these engines but is covered on its own Generation Page, as fitment and labour access vary slightly by body style.
Market Intelligence
Most Requested E90 Engines (2025)
- 1.1. M112.953 (CLK 320) — V6 petrol favourite [PATTERN DATA]
- 2.2. OM646.963 (CLK 220 CDI) — volume diesel [PATTERN DATA]
- 3.3. M113.968 (CLK 500) — V8 enthusiast choice [PATTERN DATA]
Most Requested E90 Variants
- 1.1. CLK 320
- 2.2. CLK 220 CDI
- 3.3. CLK 500 [PATTERN DATA]
Average E90 Replacement Cost
£2,200–£6,500 reconditioned, supply only [MB-QUOTE]
Most Common E90 Failures
- 1.1. M271 timing chain/supercharger clutch
- 2.2. M272/M273 balance shaft (pre-2006)
- 3.3. Hydraulic roof system leaks [PATTERN DATA]
Mercedes CLK 320 A209 (M112)
5
enquiries
Mercedes CLK 220 CDI A209 (OM646)
3
enquiries
Mercedes CLK 500 A209 (M113)
2
enquiries
FAQ
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