Is the Mercedes-Benz ML270 / ML320 CDI engine reliable?

It depends on which engine generation your M-Class has. The OM612 (W163 ML270, 1998–2005) is a robust 5-cylinder but has well-documented issues: injector seal failure (the dreaded 'black death'), low-pressure fuel pump failure, and oil leaks. The OM642 (W164 ML320, 2005–2011) is a smooth V6 but has oil cooler seal leaks, turbo actuator failure, EGR clogging and swirl flap issues. Check the Era Map above for your specific car.

What are the common problems with the Mercedes-Benz ML270 / ML320 CDI?

OM612 injector seal failure ('black death' — carbon buildup, chuffing, diesel smell), OM612 low-pressure fuel pump failure (particles damaging high-pressure pump), OM642 oil cooler seal leaks (oil loss, puddles, 'Oil Level Low' warnings), OM642 turbo actuator failure (loss of power, no boost), OM642 swirl flap failure (loss of power), and EGR clogging on both engines. The OM642's oil cooler is deep in the V of the engine, making seal replacement a big job.

Is it worth replacing a Mercedes-Benz ML270 / ML320 CDI engine, or should I scrap the car?

Apply the 70% Mercedes scrap threshold: if your M-Class is worth £4,000–£10,000 and a recon engine is £3,500–£5,000 (35–100% of the car's value), assess the overall condition carefully. Well-maintained examples with good bodywork and interior justify replacement spend. Tired examples with significant rust may not. W163 and early W164 models are becoming classics — a good engine rebuild can add value if the rest of the car is in good condition.

How do I find my Mercedes-Benz ML270 / ML320 CDI engine code?

The engine code is listed on the VIN plate and vehicle documentation. As a rule of thumb: W163 (1998–2005) ML270 CDI is OM612.963 (2.7L I5, 163 PS); W164 (2005–2007) ML320 CDI is OM642.920 (3.0L V6, 224 PS); W164 (2007–2011) ML320 CDI is OM642.820 (3.0L V6, 224 PS). Tell us your registration date and we'll confirm it for free.

Mercedes-Benz M-Class ML270 / ML320 CDI1998–20112 Engine Generations

Mercedes-Benz ML270 / ML320 CDI Engine Replacement — Compare Prices & Get Quotes

Name: Mercedes-Benz ML270 / ML320 CDI UK Engine Enquiry Data 2025
Creator: MercedesEngine.uk

The ML270 and ML320 CDI badges span two generations of Mercedes diesel — the 2.7-litre inline-five OM612 and the 3.0-litre V6 OM642. Get quotes from trusted UK Mercedes specialists for both eras, supply & fit available nationwide.

Supply & Fit Available

12-Month Warranty

Nationwide Delivery

25+ Specialists

Supply & Fit Available

12-Month Warranty

Nationwide Delivery

25+ Specialists

Mercedes-Benz ML270 / ML320 CDI Engines — from £1,500 to £7,500Common codes: OM612.963, OM642.920

Mercedes-Benz ML270 / ML320 CDI Engines — from £1,500 to £7,500· Common codes: OM612.963, OM642.920

Instant QuotesNo Obligation100% FreeReconditionedRebuiltUsedSupply & Fit AvailableUK-Wide Network

The ML270 / ML320 CDI THROUGH TIME — Era Map

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

Era Note

163 PS — robust 5-cylinder but injector "black death" and fuel pump issues

GenerationYearsEngine CodeReliabilityRecon CostEra Note

M-Class W163 (ML270 CDI) BMW 320d M-Class W163 (ML270 CDI)

1998–2005OM612.963 (2.7L I5)★★★★☆ [NEWLY ASSIGNED — see Data Note]£2,000–£5,000 [PLACEHOLDER — confirm vs cost sheet]163 PS — robust 5-cylinder but injector "black death" and fuel pump issues

M-Class W164 (ML320 CDI) BMW 320d M-Class W164 (ML320 CDI)

2005–2007OM642.920 (3.0L V6)★★★☆☆ [NEWLY ASSIGNED — see Data Note]£2,500–£6,500 [PLACEHOLDER — confirm vs cost sheet]224 PS — smooth V6 but oil cooler seals, turbo actuator and EGR issues

M-Class W164 (ML320 CDI) BMW 320d M-Class W164 (ML320 CDI)

2007–2011OM642.820 (3.0L V6)★★★☆☆ [NEWLY ASSIGNED — see Data Note]£2,800–£7,500 [PLACEHOLDER — confirm vs cost sheet]224 PS — updated OM642, same core V6 vulnerabilities

Why use this era map?

This table is the single source every other section on this page matches — Sections 2, 4 and 6 reference it rather than restating conflicting figures.

Real UK Cost Data

Verified Reliability

Expert Insights

Updated for 2025

Mercedes-Benz ML270 / ML320 CDI Engine Replacement Costs

Supply Only£2,200–£6,500

Fitted (Indie)£3,200–£8,000

Warranty12–24 months

Best ForMost owners — best cost/warranty balance

Engine TypeSupply OnlyFitted (Indie)WarrantyBest For

Used Engine£1,500–£3,000£2,300–£4,5001–6 monthsBudget priority; short-term ownership

Reconditioned Engine£2,200–£6,500£3,200–£8,00012–24 monthsMost owners — best cost/warranty balance

Rebuilt Engine£4,000–£7,500£5,000–£9,00012–24 monthsLong-term ownership; 3+ year horizon

Main Dealer New£7,000–£11,000£8,500–£13,00024–36 monthsInsurance jobs, warranty claims

Figures above reflect current market rates. A replacement engine can cost between £1,500 and £5,000 on average, with Mercedes engines typically at the higher end of the range. Used OM612 engines are available from around £1,500–£2,500. Reconditioned OM642 engines command a premium due to the complexity of the V6 design. Dealer quotes can range from £4,500 to £7,000+.

Labour estimate: Fitting an M-Class CDI engine typically takes 10–16 hours at £65–£95/hr (independent). The OM642 V6 requires more labour than the inline-five OM612. The oil cooler sits deep in the V of the OM642 engine and is a big job if the seals need replacing.

→ Compare ML270 / ML320 CDI engine prices from UK specialists

Common Problems

1. OM612 Injector Seal Failure — "Black Death" (ML270 CDI, W163 1998–2005)

Symptoms: Carbon buildup ("black death") around injectors, chuffing or ticking sound from injector area, diesel smell in cabin, rough idle, hard starting, black smoke. The copper seal underneath each injector fails, allowing combustion gases to escape and causing carbon deposits to form. The "20 cent washer on the injector fails causing black gunk to form".

Typical mileage: 80,000–150,000 miles — injectors "get tired by about 150k miles".

Repair cost: £300–£800 (injector seal replacement, seat recutting). The copper seals are "pennies from Mercedes".

Replacement cost: N/A — repair only; if ignored, injectors can seize in the head, requiring removal with a slide hammer.

🔴 Immediate - if you hear chuffing or smell diesel, book an inspection today.

Our recommendation:

The OM612's injector seals are its most common and well-documented failure. The dreaded "black death" occurs when the copper seal fails — carbon and diesel build up under the rocker cover. If caught early, the job is straightforward — replace the copper seal and recut the seat in the head. If ignored, injectors can become "properly welded in". At the first sign of chuffing, ticking or diesel smell, book an inspection immediately.

1. OM612 Injector Seal Failure — "Black Death" (ML270 CDI, W163 1998–2005)

Typical mileage: 80,000–150,000 miles — injectors "get tired by about 150k miles".

Repair cost: £300–£800 (injector seal replacement, seat recutting). The copper seals are "pennies from Mercedes".

Replacement cost: N/A — repair only; if ignored, injectors can seize in the head, requiring removal with a slide hammer.

🔴 Immediate - if you hear chuffing or smell diesel, book an inspection today.

Our recommendation:

2. OM642 Oil Cooler Seal Leak (ML320 CDI, W164 2005–2011)

Symptoms: "Check Oil Level" or "Oil Level Low" message, decreasing oil level, oil stains or puddles when parked, oil at the bottom of the transmission bell housing. The oil cooler sits deep in the V of the OM642 engine. The leak can be misdiagnosed as a rear main seal leak.

Typical mileage: 60,000–120,000 miles — a design flaw with extreme temperature and vibration. Later models have improved sealing material, but the issue is not fully removed.

Repair cost: £800–£2,500 (oil cooler seals, full seal kit, labour). A £5 part and £800–£900 labour to replace due to its location.

Replacement cost: N/A — repair only; if ignored, oil loss can lead to engine damage.

🔴 Immediate - if you see oil warnings or puddles, book an inspection today.

Our recommendation:

The OM642's oil cooler seal leak is one of the most common and serious issues on this engine. The oil cooler is located deep in the V of the engine — accessing it requires significant labour. Mercedes used gaskets of an inferior material, which after some miles and years will result in an oily mess. If you notice any oil loss or see oil stains, have the seals inspected immediately. Use the updated sealing material for replacement.

3. OM612 Low-Pressure Fuel Pump Failure (ML270 CDI, W163 1998–2005)

Symptoms: Loss of power, hard starting, fuel pump whine, engine stalling. The low-pressure fuel pump can fail, with particles damaging the high-pressure pump. Air bubbles in fuel lines due to hardened O-rings is also a common issue.

Typical mileage: 100,000–200,000 km — age-related wear.

Repair cost: £300–£800 (low-pressure fuel pump replacement, O-ring replacement).

Replacement cost: N/A — repair only; if ignored, particles can damage the high-pressure pump and injectors.

🟠 Check - book inspection urgently if symptoms appear.

Our recommendation:

The OM612's low-pressure fuel pump can fail, sending particles through the system that can damage the high-pressure pump. If you notice fuel pump whine, hard starting or loss of power, have the system inspected promptly. Replacing the low-pressure pump and O-rings is significantly cheaper than a full high-pressure pump and injector replacement.

Ready to Compare?

Get Matched With a Vetted Mercedes Specialist

25+ vetted Mercedes specialists, each experienced with the M-Class CDI range, with a 12-month warranty as standard.

Get My Free ML270 / ML320 CDI Engine Quotes Now

ML270 / ML320 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.

ML270 / ML320 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 SenseOM612 injector seal leak ("black death")✅ Yes£300–£800Catch early — copper seals are cheap, labour is moderateOM612 low-pressure fuel pump failure✅ Yes£300–£800Essential repair — prevent damage to high-pressure pumpOM642 oil cooler seal leak✅ Yes£800–£2,500Essential repair — catch before oil loss damages engineOM642 turbo actuator failure✅ Yes£200–£1,500Actuator refurbishment is cost-effective; full turbo if damagedOM642 swirl flap failure✅ Yes£500–£1,200Swirl flaps can stick or break — repair to restore powerSnapped timing chain (any engine)❌ Usually NoEngine replacementInterference engine — piston-valve contact means little is left to repair

Buying This ML270 / ML320 CDI? Check These First

Buy If

W163 ML270 (OM612) with full service history and no injector "black death" — robust 5-cylinder
OM612 with injector seals already replaced and no fuel pump issues
W164 ML320 (OM642) with oil cooler seals replaced with updated material
Full service history with regular oil changes (every 8,000–10,000 miles)

Avoid If

OM612 with chuffing or ticking from injectors — "black death" injector seal failure
OM612 with fuel pump whine or hard starting — low-pressure fuel pump failure
OM642 with oil leaks or "Oil Level Low" warnings — oil cooler seals are failing
OM642 with loss of power or boost — turbo actuator or swirl flap issues

Closing Verdict

The M-Class CDI range spans two distinct engine families. The OM612 (ML270, W163 1998–2005) is a robust 5-cylinder but has well-documented injector seal and fuel pump issues. The OM642 (ML320, W164 2005–2011) is a smooth V6 but has oil cooler seal, turbo actuator and swirl flap vulnerabilities. With the 70% Mercedes scrap threshold, a £3,500–£5,000 reconditioned engine on an M-Class valued at £4,000–£10,000 is 35–100% of the car's value — assess the overall condition carefully. W163 and early W164 models are becoming classics; a good engine rebuild can add value if the rest of the car is in good condition.

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

→ Compare ML270 / ML320 CDI engine prices before you buy

Don't Guess. Compare.

Get real quotes from vetted UK specialists and make the right call for your 320d.

→ Compare ML270 / ML320 CDI engine prices before you buy

20+ Vetted Specialists UK Network

12-Month Warranty as Standard

Nationwide Delivery & Collection

Transparent Pricing, No Hidden Fees

Thousands of 320d Owners Helped

Buying Checklist

Before you buy a used Mercedes-Benz ML270 / ML320 CDI (or before you commit to an engine replacement), check these:

Injector Seals — On OM612, check for carbon buildup around injectors ("black death") and listen for chuffing or ticking

Fuel Pump — On OM612, listen for fuel pump whine; check for hard starting

Cold Start — Listen for rattling on startup (timing chain wear on both engines)

Oil Level — On OM642, check for "Oil Level Low" warnings or oil puddles (oil cooler seal leak)

Service History — Including which engine era (OM612/OM642) and oil-interval discipline

Turbo Check — On OM642, test acceleration for power loss or boost issues (turbo actuator)

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

MOT History — Check for emissions-related failures

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.

OM612.963 (2.7L I5)

Years1998–2005

Power163 PS (120 kW)

2025 Enquiries— (pattern data)

Avg. Recon Cost£2,000–£5,000 [PLACEHOLDER]

Engine CodeYearsPower2025 EnquiriesAvg. Recon Cost

OM612.963 (2.7L I5)1998–2005163 PS (120 kW)— (pattern data)£2,000–£5,000 [PLACEHOLDER]

OM642.920 (3.0L V6)2005–2007224 PS (165 kW)— (pattern data)£2,500–£6,500 [PLACEHOLDER]

OM642.820 (3.0L V6)2007–2011224 PS (165 kW)— (pattern data)£2,800–£7,500 [PLACEHOLDER]

Technical Specs

OM642.820 — W164 ML320 CDI

Displacement2,685 cc

Cylinders5-cylinder inline, 20-valve

Bore x Stroke88.0 x 88.3 mm

Compression Ratio18.0:1

Fuel SystemCommon-rail CDI

TurbochargerVGT turbocharger

Torque370 Nm @ 1,600–2,800 rpm

Displacement2,987 cc

CylindersV6, 72° V, 24-valve

Bore x Stroke83.0 x 92.0 mm

Compression Ratio16.5:1

Fuel SystemCommon-rail CDI

TurbochargerVGT turbocharger

Torque510 Nm @ 1,600–2,800 rpm

→ Compare ML270 / ML320 CDI engine prices for your Mercedes

Get quotes from trusted UK specialists in minutes.

Market Intelligence

Most Common Failure

OM612 injector seal "black death" (W163) / OM642 oil cooler seal leak (W164) — generation-dependent 【PATTERN DATA】

Average Enquiry Mileage

85,000

miles 【PATTERN DATA】

Average Replacement Cost

£3,500

reconditioned, supply only 【PLACEHOLDER — confirm vs cost sheet】

Most Requested Engine Code

OM642 (W164 ML320 CDI — highest-volume generation) 【PATTERN DATA】

Peak Enquiry Season

Autumn/Winter — cold starts expose injector and timing chain issues 【PATTERN DATA】

Regional Demand

South East22%

London18%

North West (14%) 【PATTERN DATA】

Regional Demand Breakdown

22%South East

18%London

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.

Why UK Mercedes-Benz ML270 / ML320 CDI Owners Trust MercedesEngine.uk

Trusted ML270 / ML320 CDI Engine Suppliers
every garage and engine rebuilder in our network is vetted, rated and reviewed by real M-Class owners, with specialists who understand the OM612's injector seal and fuel pump issues and the OM642's oil cooler seal, turbo actuator and swirl flap vulnerabilities intimately, across every engine generation.
Compare ML270 / ML320 CDI Engine Replacement Companies
see prices, warranty terms and supply & fit options side-by-side before you commit, all from specialists experienced with Mercedes' diesel engines and their specific maintenance requirements.
UK Engine Replacement Services for M-Class CDI
supply-only or full supply & fit available nationwide, covering everything from injector seal replacement to oil cooler repair to full engine swaps on your W163 or W164 M-Class.

Find the best Mercedes-Benz ML270 / ML320 CDI engine replacement UK drivers rely on. Compare prices from trusted specialists on MercedesEngine.uk today and get your M-Class back on the road with confidence.

Compare Mercedes-Benz ML270 / ML320 CDI Engine Prices Now

100% Free

No hidden fees

No Obligation

Get quotes with zero pressure

UK Specialists

20+ vetted experts

12-Month Warranty

As standard

Nationwide Delivery

Supply & fit available

100% Free

No hidden fees

No Obligation

Get quotes with zero pressure

UK Specialists

20+ vetted experts

12-Month Warranty

As standard

Nationwide Delivery

Supply & fit available