Is the Mercedes-Benz CLK 200 CDI / 220 CDI engine reliable?

The OM611 and OM646 are robust and economical diesels, but they have well-documented weaknesses. Injector seal failure ('Black Death') is the most common issue on both engines. Later OM646 engines can suffer from DPF and EGR problems. With good maintenance, these engines are capable of high mileage.

What are the common problems with the Mercedes-Benz CLK 200 CDI and 220 CDI?

Injector seal failure ('Black Death' — tar-like sludge around injectors), DPF and EGR clogging (OM646), inlet manifold flap problems (OM611), timing chain stretch, and oil dilution from failed DPF regenerations. The injector seals are the most critical concern.

Is it worth replacing a Mercedes-Benz CLK 200/220 CDI engine, or should I scrap the car?

CLK values range from £2,000–£10,000 depending on condition and spec. A £2,000–£5,000 reconditioned engine is 20–50% of the vehicle's value — apply the Mercedes 70% scrap threshold. If the car is a cherished example with good bodywork, replacement is often worthwhile.

How do I find my Mercedes-Benz CLK 200 CDI or 220 CDI engine code?

Listed on the VIN plate and vehicle documentation. C208/A208 (1998–2002) uses OM611.962; C209/A209 (2002–2009) uses OM646.963 (200 CDI) or OM646.963/.966 (220 CDI). Tell us your registration date and we'll confirm it for free.

Can I repair the 'Black Death' injector seals, or does the engine need replacement?

The injector seals can be replaced — they are wear items. Replacement costs £300–£800 and requires specialist tools to re-cut the injector seats. If the injector has seized in the head, extraction can be difficult and expensive. A preventative seal replacement is far cheaper than a full engine replacement. At the first sign of ticking or black sludge around the injectors, book an inspection immediately.

Mercedes-Benz CLK 200/220 CDI1998–20092 Engine Generations

Mercedes-Benz CLK 200 CDI / 220 CDI Engine Replacement — Compare Prices & Get Quotes

Name: Mercedes-Benz CLK 200/220 CDI UK Engine Enquiry Data 2025
Creator: MercedesEngine.uk

The CLK 200 CDI and 220 CDI are powered by Mercedes' first-generation common-rail diesels — the OM611 in earlier cars and the improved OM646 in later models. They're smooth, economical and torquey, but injector seal failures (Black Death), EGR/DPF issues and inlet flap problems are well-documented. Get quotes from UK specialists for reconditioned, rebuilt and used units today.

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Mercedes-Benz CLK 200/220 CDI Engines — from £1,500 to £6,500Common codes: OM611, OM646

Mercedes-Benz CLK 200/220 CDI Engines — from £1,500 to £6,500· Common codes: OM611, OM646

Instant QuotesNo Obligation100% FreeReconditionedRebuiltUsedSupply & Fit AvailableUK-Wide Network

The CLK CDI THROUGH TIME — Era Map

Four generations. Four eras. One guide to reliability, costs and what really matters.

GenerationYearsEngine CodeReliabilityRecon CostEra Note

Why use this era map?

Every cost guide, reliability rating and engine code on this page is aligned to the data above. This keeps everything consistent and trustworthy.

Real UK Cost Data

Verified Reliability

Expert Insights

Updated for 2025

Mercedes-Benz CLK 200/220 CDI Engine Replacement Costs

Supply Only£2,000–£5,000

Fitted (Indie)£3,500–£6,500

Warranty12–24 months

Best ForMost owners — best cost/warranty balance

Engine TypeSupply OnlyFitted (Indie)WarrantyBest For

Used Engine£1,500–£3,000£2,500–£4,5001–6 monthsBudget priority; older OM611 examples

Reconditioned Engine£2,000–£5,000£3,500–£6,50012–24 monthsMost owners — best cost/warranty balance

Rebuilt Engine£3,500–£6,500£5,000–£8,50012–24 monthsLong‑term ownership; 3+ year horizon

Main Dealer NewN/A — no longer availableN/A—N/A — specialist rebuild only

Figures above reflect the current CLK CDI market. A reconditioned engine typically costs £1,200–£2,200 supply only, with total installed cost around £1,800–£2,800. OM646 engines command a slight premium over OM611 units. See the Era Map above for generation-specific context.

Labour estimate: Fitting a CLK CDI engine typically takes 10–14 hours at £65–£95/hr (independent) or £110–£160/hr (London/SE dealer). The longitudinal layout makes access relatively straightforward.

→ Compare CLK CDI engine prices from UK specialists

Common Problems

1. Injector Seal Failure ("Black Death") — OM611 & OM646

Symptoms: Ticking or chuffing noise from the top of the engine, diesel smell inside or around the car, rough idle, loss of power, hard starting, thick black tar-like sludge around the injectors

Typical mileage: 60,000–120,000 miles

Repair cost: £300–£800 (injector seal replacement and seat re-cutting)

Replacement cost: £2,000–£4,500 (if injector seizure damages the cylinder head)

🔴 Immediate - injector seal failure is the defining issue on both OM611 and OM646 engines

Our recommendation:

Mercedes CDI engines are notoriously susceptible to "Black Death" — a condition where injector seals fail, allowing combustion gases to escape past the injectors. The escaping gases create a thick, tar-like sludge around the affected injectors. If left unchecked, the injector can seize in the head, requiring expensive extraction work. Lift the engine cover and inspect the area around each injector for black sludge — any sign of leakage requires immediate attention. Replacement of the seals and re-cutting of the injector seats is a specialist job.

Read the full injector seal failure guide

1. Injector Seal Failure ("Black Death") — OM611 & OM646

Symptoms: Ticking or chuffing noise from the top of the engine, diesel smell inside or around the car, rough idle, loss of power, hard starting, thick black tar-like sludge around the injectors

Typical mileage: 60,000–120,000 miles

Repair cost: £300–£800 (injector seal replacement and seat re-cutting)

Replacement cost: £2,000–£4,500 (if injector seizure damages the cylinder head)

🔴 Immediate - injector seal failure is the defining issue on both OM611 and OM646 engines

Our recommendation:

Read the full injector seal failure guide

2. DPF and EGR System Problems — OM646 (2004+)

Symptoms: DPF warning light, limp mode, poor fuel economy, failed regenerations, oil dilution (rising oil level)

Typical mileage: 50,000–100,000 miles

Repair cost: £400–£1,200 (DPF cleaning or EGR valve replacement)

Replacement cost: £2,200–£4,500 (if DPF failure causes engine damage)

🟠 Check - book inspection urgently

Our recommendation:

Later OM646 engines fitted with DPFs and EGR systems are prone to clogging, particularly if the car is used for short journeys. Failed DPF regenerations can cause oil dilution and rising oil levels. If the DPF warning light appears, take the car for a sustained motorway run to allow regeneration. If the issue persists, have the DPF and EGR system inspected. Regular motorway driving is essential for these engines.

Read the full DPF and EGR failure guide

3. Inlet Manifold Flap Problems — OM611 (Early)

Symptoms: Loss of power, rough idle, engine warning light, poor fuel economy, hesitation on acceleration

Typical mileage: 80,000–150,000 miles

Repair cost: £300–£800 (inlet manifold flap replacement or repair)

Replacement cost: £2,000–£4,000 (if flap failure causes engine damage)

🟡 Monitor - book inspection soon

Our recommendation:

Early OM611 engines can suffer from inlet manifold flap problems. The flaps can become stuck or break, causing loss of power and poor running. Replacement of the inlet manifold is the usual fix. Some owners choose to delete the flaps entirely, though this may affect emissions compliance. If you experience hesitation or loss of power, have the inlet manifold inspected.

Read the full inlet manifold failure guide

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CLK 200/220 CDI — Repair, Buy, or Replace?

Every 320d has a story. Make the right call with clear data, real-world costs, and honest guidance from UK specialists.

CLK 200/220 CDI — Repair, Buy, or Replace?

Every 320d has a story. Make the right call with clear data, real-world costs, and honest guidance from UK specialists.

Can It Be Repaired?

ProblemRepairable?Typical CostWhen It Makes SenseInjector seal failure ("Black Death")✅ Yes£300–£800Catch early; seat re-cutting may be requiredInjector seizure (head damage)⚠️ Sometimes£2,000–£4,500Viable on a cherished example; borderline on high-mileageDPF clogging (OM646)✅ Yes£400–£1,200Forced regeneration or cleaning — prevention is keyEGR valve failure✅ Yes£400–£1,200Replacement — restore performance and emissionsInlet manifold flap failure (OM611)✅ Yes£300–£800Replace manifold or delete flapsTiming chain stretch✅ Yes£800–£2,000Labour-intensive but cheaper than a full engine

Buying This CLK 200/220 CDI? Check These First

Buy If

Post-2004 OM646 with documented DPF and injector service history
OM611 with evidence of injector seal work — the defining weakness addressed
Full service history with correct MB-spec oil
Evidence of regular motorway driving (essential for DPF health)

Avoid If

Any ticking or chuffing from the top of the engine — injector seal "Black Death" is likely
Black tar-like sludge around the injectors — injector seal failure is imminent
DPF warning light or limp mode — regeneration issues are expensive to fix
Poor service history — both engines are unforgiving of neglect

Closing Verdict

The CLK 200 CDI and 220 CDI are powered by Mercedes' first-generation common-rail diesels — smooth, economical and torquey. The OM611 (1998–2002) is a robust engine with injector seal and inlet flap issues. The OM646 (2002–2009) is the refined successor with improved injection pressure, but DPF and EGR problems on later cars. Both suffer from the notorious "Black Death" injector seal failure — inspect the injector area carefully before buying. Buy on history, maintain on schedule, and the CLK CDI will reward you with effortless cruising.

Don't guess.Get the right engine at the right price.

→ Compare CLK CDI engine prices before you buy

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Buying Checklist

Before you buy a used Mercedes-Benz CLK 200 CDI or 220 CDI (or before you commit to an engine replacement), check these:

1. Injector Area — Lift the engine cover and check for black tar-like sludge around the injectors ("Black Death" — the most critical check on both OM611 and OM646)

2. Cold Start — Any ticking or chuffing from the top of the engine? (injector seal warning)

3. Service History — including which generation (OM611 or OM646) and evidence of injector work

4. DPF Health (OM646) — Any warning lights or reduced power? (DPF clogging is common)

5. Oil Level — Is the oil level rising? (oil dilution from failed DPF regenerations)

6. Performance — Any hesitation or loss of power? (inlet flap or EGR issues)

7. Engine Warning Light — Have codes been read? Any unresolved issues?

8. MOT History — Check for emissions-related failures (DPF, EGR, NOx sensors)

Buy smart. Drive with confidence.

A few checks today can save thousands tomorrow. Use this checklist to avoid the most common 320d pitfalls.

Buy smart. Drive with confidence.

A few checks today can save thousands tomorrow. Use this checklist to avoid the most common 320d pitfalls.

Engine Codes

This table's rows match Section 1B's Era Map exactly — two engine families across the CLK CDI's history.

OM611.962

Years1998–2002

Power102–116 PS

2025 Enquiries[PATTERN DATA]

Avg. Recon Cost£2,000–£4,000 [MB-QUOTE]

Engine CodeYearsPower2025 EnquiriesAvg. Recon Cost

OM611.9621998–2002102–116 PS[PATTERN DATA]£2,000–£4,000 [MB-QUOTE]

OM646.9632002–2009122 PS[PATTERN DATA]£2,200–£4,500 [MB-QUOTE]

OM646.963/.9662002–2009136–150 PS[PATTERN DATA]£2,500–£5,000 [MB-QUOTE]

Technical Specs

OM646 — 220 CDI

Displacement2,148cc (2.1‑litre)

Cylinders4-cylinder inline

Bore x Stroke88.0 x 88.3 mm

Compression Ratio18.0:1

Fuel SystemCommon-rail direct injection (Bosch 3-plunger pump)

ValvetrainDOHC, 4 valves per cylinder, duplex roller chain

Displacement2,148cc (2.1‑litre)

Cylinders4-cylinder inline

Bore x Stroke88.0 x 88.3 mm

Compression Ratio18.0:1

Fuel SystemCommon-rail direct injection

Rated Output110 kW / 150 hp

Rated Torque340 Nm

→ Compare CLK CDI engine prices for your Mercedes

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Market Intelligence

Most Common Failure

Injector seal failure ("Black Death") — the defining risk on both OM611 and OM646 engines

Average Enquiry Mileage

OM611: 80,000–150,000 miles / OM646: 60,000–120,000 miles【PATTERN DATA】

Average Replacement Cost

£2,000

–£5,000 reconditioned, supply only depending on generation【MB-QUOTE】

Most Requested Engine Code

OM646 — the later, more refined CLK diesel【PATTERN DATA】

Peak Enquiry Season

Spring — convertible and coupe season【PATTERN DATA】

Regional Demand

London20%

South East18%

South West (14%)【PATTERN DATA】

Regional Demand Breakdown

20%London

18%South East

Frequently Asked Questions

All prices are indicative UK market ranges based on historical quote data from our network of engine specialists. Actual costs vary by variant, engine code, damage severity and workshop location. Use our free comparison tool to get tailored quotes. Every engine supplied through EnginesMarket carries a minimum 12-month unlimited-mileage warranty — always confirm terms with your chosen supplier.

Trusted CLK CDI Engine Suppliers
every garage and engine rebuilder in our network is vetted, rated and reviewed by real CLK 200 and 220 CDI owners, as part of the Engine Finders network, across both the OM611 and OM646 generations.
Compare CLK CDI Engine Replacement Companies
see prices, warranty terms and supply & fit options side‑by‑side before you commit, with specialists who genuinely understand the OM611/OM646's injector seal ("Black Death"), DPF/EGR and inlet flap nuances.
UK Engine Replacement Services for CLK CDI
supply‑only or full supply & fit available nationwide, covering Mercedes' first-generation CDI coupes and convertibles with a 12‑month warranty as standard.

Find the best Mercedes-Benz CLK 200 CDI or 220 CDI engine replacement UK owners trust. Compare prices from trusted specialists on MercedesEngine.uk today and keep your CLK on the road.

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