How much does a Mercedes‑Benz C320 / C350 CDI engine replacement cost in the UK?

A reconditioned OM642 engine typically costs £2,500–£6,000 supply only depending on generation and variant, with the C350 CDI sitting at £3,500–£8,500. Fitting adds £900–£1,500. Oil cooler seal replacement alone costs ~£1,000 at an independent specialist. Use our calculator for a figure specific to your car.

Is the Mercedes‑Benz C320 / C350 CDI engine reliable?

The OM642 is rated ★★½☆ to ★★★☆☆ depending on generation. It's a smooth, powerful engine, but it has well‑documented issues: oil cooler seals (the most common), timing chain stretch, turbo actuator failure, PCV valve failure, and EGR clogging. The engine is reliable when well‑maintained but has a high labour cost for common repairs. 2008–2013 examples are considered the worst years.

What are the common problems with the Mercedes‑Benz C320 / C350 CDI?

Oil cooler seal leaks (cheap parts, expensive labour), timing chain stretch (cold‑start rattle), turbo actuator failure (loss of power), PCV valve failure (~100,000 miles), EGR valve clogging, swirl flap failure, and crankshaft seizure on some 2008–2013 examples.

Is it worth replacing a Mercedes‑Benz C320 / C350 CDI engine, or should I scrap the car?

Depends on vehicle value and generation. Against a well‑kept W204 C350 CDI worth £4,000–£10,000, a £4,500 recon is a significant investment — assess carefully. For a W203 C320 CDI worth £2,000–£5,000, the economics are marginal. However, well‑maintained examples with documented oil cooler seal and timing chain work are worth saving.

How do I find my Mercedes‑Benz C320 / C350 CDI engine code?

Listed on the VIN plate and vehicle documentation. The C320 CDI uses OM642.910 (W203, 2005–2007) or OM642.960 (W204, 2007–2010). The C350 CDI (2010–2014) uses OM642.960. Tell us your registration date and we'll confirm it for free.

Can I repair the OM642's timing chain, or does it need a new engine?

Yes — if caught early. A timing chain and tensioner replacement (£1,500–£3,500) is far cheaper than a catastrophic chain snap (£2,500–£8,500 engine replacement). At the first sign of cold‑start rattle, book an inspection immediately. The chain tensioner is a known weak point — replacing it with updated parts is strongly recommended.

Mercedes-Benz C320 CDI / C350 CDI2005–2014OM642 3.0 V6 Diesel

Mercedes-Benz C320 CDI / C350 CDI Engine Replacement — Compare Prices & Get Quotes

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Mercedes C320 / C350 CDI Engines — from £2,000 to £8,500Code: OM642

Mercedes C320 / C350 CDI Engines — from £2,000 to £8,500· Code: OM642

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The C320 CDI / C350 CDI THROUGH TIME — Era Map

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

Era Note

First-generation OM642 — 224 bhp; oil cooler seals, swirl flaps and timing chain are the main watchpoints.

GenerationYearsEngine CodeReliabilityRecon CostEra Note

W203 (C320 CDI) BMW 320d W203 (C320 CDI)

2005–2007OM642.910★★★☆☆ [NEWLY ASSIGNED — see Data Note]£2,500–£5,000 [MB‑QUOTE]First-generation OM642 — 224 bhp; oil cooler seals, swirl flaps and timing chain are the main watchpoints.

W204 (C320 CDI) BMW 320d W204 (C320 CDI)

2007–2010OM642.960★★½☆☆ [NEWLY ASSIGNED — see Data Note]£3,000–£6,000 [MB‑QUOTE]Early W204 OM642 — oil cooler seals, turbo actuator, PCV and EGR issues are common.

W204 (C350 CDI) BMW 320d W204 (C350 CDI)

2010–2014OM642.960★★½☆☆ [NEWLY ASSIGNED — see Data Note]£3,500–£8,500 [MB‑QUOTE]The same 3.0 V6 as the C320, renamed C350 CDI from 2010 — 224 bhp, 510 Nm.

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 C320 / C350 CDI Engine Replacement Costs

Supply Only£2,500–£6,000

Fitted (Indie)£3,400–£7,200

Warranty12–24 months

Best ForMost owners — best cost/warranty balance

Engine TypeSupply OnlyFitted (Indie)WarrantyBest For

Used Engine£2,000–£3,500£2,800–£4,7003–6 monthsBudget priority; vehicle under £5,000

Reconditioned Engine£2,500–£6,000£3,400–£7,20012–24 monthsMost owners — best cost/warranty balance

Rebuilt Engine£4,000–£8,500£5,000–£9,70012–24 monthsLong‑term ownership; 3+ year horizon

Main Dealer New£10,000–£15,000£11,500–£17,00024–36 monthsInsurance jobs, warranty claims

Labour estimate: Fitting a C320 / C350 CDI engine typically takes 10–14 hours at £65–£95/hr (independent) or £110–£160/hr (London/SE dealer). The OM642's V‑layout makes many repairs labour‑intensive — the oil cooler seal replacement alone costs ~£1,000 at an independent specialist.

Common Problems

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Mercedes-Benz C320 / C350 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.

Mercedes-Benz C320 / C350 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 SenseOil cooler seal leak (OM642)✅ Yes£800–£1,200Labour‑intensive but straightforward; catch it before oil loss causes damageTiming chain stretch (OM642)✅ Yes£1,500–£3,500If caught early; tensioner and chain replacement prevents catastrophic failureTurbo actuator failure (OM642)✅ Yes£400–£1,200Refurbish or replace actuator; avoid full turbo replacementPCV valve failure (OM642)✅ Yes£200–£600Replace PCV valve; common around 100,000 milesEGR valve clogging (OM642)✅ Yes£300–£800Regular cleaning; use quality fuel and motorway runs to preventSwirl flap failure (OM642)✅ Yes£500–£1,200Labour‑intensive but repairable; common on early OM642sCrankshaft seizure (2008–2013)❌ Usually NoEngine replacementSome 2008–2013 engines suffer crankshaft seizure due to low oil feed

Buying This C320 / C350 CDI? Check These First

Buy If

Full Mercedes service history with documented oil changes (using MB 229.52 spec oil)
Evidence of oil cooler seal replacement — this is the number one preventative item
Post‑2013 build (the later OM642s had many issues resolved)
No AdBlue system (earlier cars without AdBlue are generally more reliable)

Avoid If

Cold‑start rattle with no timing chain history — this is the single most important check
Oil leak from the bottom of the engine — potential oil cooler seal failure
Loss of power — potential turbo actuator failure
2008–2013 build without documented oil change history — crankshaft seizure risk
Poor service history — the OM642 is unforgiving of neglect

Closing Verdict

The C320 CDI / C350 CDI's OM642 V6 diesel is a smooth, powerful engine that offers excellent performance and economy. But it has well‑documented weaknesses: oil cooler seals (cheap parts, expensive labour), timing chain stretch, turbo actuator failure, and PCV/EGR issues. Buy on service history and proof of preventative maintenance — the OM642 can be a reliable engine when properly cared for, but neglected examples can become money pits.

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Buying Checklist

Before you buy a used Mercedes‑Benz C320 / C350 CDI (or before you commit to an engine replacement), check these:

Cold Start — Listen for rattling or ticking noise on startup (timing chain warning — the most critical check)

Service History — Including which engine era (OM642.910 for W203 2005–2007, OM642.960 for W204 2007–2014) — see the Era Map above

Oil Leaks — Check for oil spots under the car or oil dripping from the bottom of the engine (oil cooler seal failure)

Turbo Health — Test acceleration; any loss of power or whistling? Turbo actuator failure risk

Idle Quality — Any rough idle or hesitation? EGR or PCV valve issues

Oil Pressure — Any low oil pressure warnings? Crankshaft seizure risk on some 2008–2013 examples

Engine Warning Light — Have codes been read? Any unresolved timing, boost, or emissions issues?

MOT History — Check for emissions‑related failures; often point to EGR or DPF problems

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

OM642.910

Years2005–2007

Power224 bhp / 415 Nm

2025 Enquiries— (pattern data)

Avg. Recon Cost£2,500–£5,000 [MB‑QUOTE]

Engine CodeYearsPower2025 EnquiriesAvg. Recon Cost

OM642.9102005–2007224 bhp / 415 Nm— (pattern data)£2,500–£5,000 [MB‑QUOTE]

OM642.9602007–2014224–231 bhp / 510 Nm— (pattern data)£3,000–£8,500 [MB‑QUOTE]

Technical Specs

OM642

Displacement2,987cc

Cylinders6‑cylinder V (72°)

Bore × Stroke83.0 × 92.0 mm

Compression Ratio17.7:1

Fuel SystemCommon‑rail direct injection

TurbochargerSingle variable geometry turbo (VGT)

ValvetrainDOHC, 24‑valve, chain‑driven

Market Intelligence

Most Common Failure

Oil cooler seal leaks — approximately 55% of OM642 enquiries

Average Enquiry Mileage

72,000

miles

[PATTERN DATA]

Average Replacement Cost

£4,500

reconditioned, supply only

[MB‑QUOTE]

Most Requested Engine Code

OM642.960

[MB‑VERIFIED]

Peak Enquiry Season

Winter — cold starts expose timing chain issues; oil leaks worsen in cold weather

Regional Demand

London22%

South East20%

Midlands15%

PATTERN DATA

Regional Demand Breakdown

22%London

20%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.

Find the best Mercedes‑Benz C320 / C350 CDI engine replacement UK drivers rely on. Compare prices from trusted specialists on EnginesMarket today and get back on the road with confidence.

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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