What are the common problems with the Mercedes A-Class A160/A170 CDI?

The most common issues are turbocharger failure (the defining weakness of the OM668), fuel injector and fuel system problems (rough idle, misfires, stalling), oil leaks from the heat exchanger and injection pump, and EGR valve failure.

Is it worth replacing an A-Class CDI engine, or should I scrap the car?

Depends on vehicle value and condition. Against a tidy £1,500–£4,000 A-Class, a £1,200–£2,800 recon is 30‑75% of the car's value – often worth it on well‑maintained examples. If the turbo has failed or the engine has suffered major internal failure, get a full diagnostic assessment before committing.

How do I find my A-Class's engine code?

The OM668 engine code is stamped on the engine block and listed on your V5C. The A160 CDI uses the OM668.941 (60 PS, 1998‑2001) or OM668.940 (75 PS, 2001‑2004). The A170 CDI uses the OM668.940 (90 PS, 1998‑2001) or OM668.942 (95 PS, 2001‑2004).

Can I repair an A-Class CDI engine issue, or does it need replacement?

Most issues – turbocharger failure, fuel injector problems, oil leaks, EGR valve failure – are repairable. However, if the engine suffers major internal failure (crank, bearings), a full engine replacement is usually more cost‑effective than a rebuild. The OM668 is a durable engine when properly maintained.

Mercedes A-Class A160/A170 CDI1998–20041.7L Turbo Diesel (OM668)

Mercedes A-Class A160 / A170 CDI Engine Replacement — Compare Prices & Get Quotes

Name: Mercedes A-Class CDI UK Engine Enquiry Data 2025
Creator: MercedesEngine.uk

Get quotes today from trusted UK Mercedes specialists. Compare reconditioned, rebuilt and used OM668 1.7-litre turbo diesel engines for the A-Class A160 and A170 CDI — the efficient, durable diesel that powered Mercedes' pioneering compact hatchback. Supply & fit available nationwide.

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Mercedes A-Class CDI Engines — from £800 to £2,800Engine code: OM668 (A160/A170 CDI)

Mercedes A-Class CDI Engines — from £800 to £2,800· Engine code: OM668 (A160/A170 CDI)

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Mercedes A-Class A160/A170 CDI — Which Engine Does Your Car Actually Have?

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

Era Note

60 PS, 160 Nm — no intercooler, the entry-level CDI

GenerationYearsEngine CodeReliabilityRecon CostEra Note

W168 (A160 CDI) BMW 320d W168 (A160 CDI)

1998–2001OM668.941 (DE17A)★★★☆☆ [NEWLY ASSIGNED — see Data Note]£1,200–£2,000 [PLACEHOLDER — confirm vs cost sheet]60 PS, 160 Nm — no intercooler, the entry-level CDI

W168 (A160 CDI) BMW 320d W168 (A160 CDI)

2001–2004OM668.940 (DE17LA Red)★★★½☆ [NEWLY ASSIGNED — see Data Note]£1,400–£2,200 [PLACEHOLDER — confirm vs cost sheet]75 PS, 160 Nm — intercooler added, improved power

W168 (A170 CDI) BMW 320d W168 (A170 CDI)

1998–2001OM668.940 (DE17LA)★★★½☆ [NEWLY ASSIGNED — see Data Note]£1,600–£2,500 [PLACEHOLDER — confirm vs cost sheet]90 PS, 180 Nm — the original A170 CDI, 13s 0-100 km/h

W168 (A170 CDI) BMW 320d W168 (A170 CDI)

2001–2004OM668.942 (DE17LA)★★★★☆ [NEWLY ASSIGNED — see Data Note]£1,800–£2,800 [PLACEHOLDER — confirm vs cost sheet]95 PS, 180 Nm — latest OM668, most refined and reliable

Why use this era map?

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

Real UK Cost Data

Verified Reliability

Expert Insights

Updated for 2025

Mercedes A-Class A160/A170 CDI Engine Replacement Costs

Supply Only£1,400–£2,400

Fitted (Indie)£2,400–£3,800

Warranty12–24 months

Best ForMost owners — best cost/warranty balance

Engine TypeSupply OnlyFitted (Indie)WarrantyBest For

Used Engine£800–£1,500£1,400–£2,5001–6 monthsBudget priority; short‑term ownership

Reconditioned Engine£1,400–£2,400£2,400–£3,80012–24 monthsMost owners — best cost/warranty balance

Rebuilt Engine£2,000–£2,800£3,000–£4,20012–24 monthsLong‑term ownership; maximum reliability

Main Dealer NewN/A (NLA from Mercedes)N/AN/ANot available — all engines are rebuilt or used

Figures above reflect the W168 A-Class CDI pricing. A replacement OM668 engine costs on average £819 in good condition, with new or reconditioned units costing up to £2,524. Reconditioned engine costs typically range from £1,200–£2,200, with total installed cost around £1,800–£2,800.

Labour estimate: Fitting an A-Class CDI engine typically takes 10‑14 hours at £75‑£110/hr (independent Mercedes specialist). The engine's sandwich‑concept mounting and transverse orientation add complexity. There is little space under the hood, and for servicing the diesel engine must be lowered with a subframe.

→ Compare A-Class CDI engine prices from UK specialists

Common Problems

1. Turbocharger Failure

Symptoms: Loss of power, excessive black smoke from the exhaust, whistling or grinding noise from the engine bay, engine warning light, reduced fuel economy, poor acceleration.

Typical mileage: 80,000–130,000 miles (130,000 km).

Repair cost: £600–£1,500 [PLACEHOLDER] (turbocharger replacement — BorgWarner K03 unit).

Replacement cost: N/A — repair only (if caught early; ignored turbo failure can send debris into the engine).

🟠 Check - book inspection urgently if you notice power loss or unusual noises.

Our recommendation:

The turbocharger is a known weak point on the OM668, with a lifespan that rarely exceeds 130,000 km. The BorgWarner K03 turbocharger can suffer from bearing wear and oil seal failure. Regular oil changes (using the correct 5W-30 or 10W-40 fully synthetic diesel engine oil) are essential to prolong turbo life. If you notice a sudden loss of power or unusual noises from the engine bay, have the turbocharger inspected immediately.

1. Turbocharger Failure

Symptoms: Loss of power, excessive black smoke from the exhaust, whistling or grinding noise from the engine bay, engine warning light, reduced fuel economy, poor acceleration.

Typical mileage: 80,000–130,000 miles (130,000 km).

Repair cost: £600–£1,500 [PLACEHOLDER] (turbocharger replacement — BorgWarner K03 unit).

Replacement cost: N/A — repair only (if caught early; ignored turbo failure can send debris into the engine).

🟠 Check - book inspection urgently if you notice power loss or unusual noises.

Our recommendation:

2. Fuel Injector & Fuel System Issues

Symptoms: Rough idling, misfires, poor engine performance, increased fuel consumption, hard starting, engine stalling, fuel leaks from the injection pump.

Typical mileage: 80,000–150,000 miles.

Repair cost: £300–£800 [PLACEHOLDER] (injector cleaning or replacement).

Replacement cost: N/A — repair only.

🟠 Check - book inspection urgently if rough running or stalling occurs.

Our recommendation:

Clogged fuel injectors can lead to poor engine performance and increased fuel consumption. Malfunctioning injectors may cause rough idling and misfires. The Bosch fuel system is generally reliable, but the fuel pressure regulator can fail. If the engine stalls or runs rough, check for injector leak-off or fuel pressure issues. Regular use of quality diesel and occasional fuel system cleaner can help prevent injector issues.

3. Oil Leaks — Heat Exchanger & Injection Pump

Symptoms: Oil spots under the vehicle, burning oil smell, low oil level warning, visible oil leak from the engine bay.

Typical mileage: 60,000–120,000 miles (age‑related).

Repair cost: £200–£600 [PLACEHOLDER] (seal or gasket replacement).

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

🟠 Check - book inspection urgently if oil leak is detected.

Our recommendation:

Oil leaks are a common issue on the OM668, particularly through the heat exchanger seals and from the injection pump. If you notice oil spots under your A-Class or a burning oil smell, investigate immediately. These leaks are usually repairable with new seals or gaskets. Regular oil level checks are essential to prevent low oil pressure and engine damage.

4. EGR Valve Failure

Symptoms: Reduced power, rough idle, increased fuel consumption, engine warning light, black smoke from exhaust.

Typical mileage: 60,000–100,000 miles.

Repair cost: £200–£500 [PLACEHOLDER] (EGR valve cleaning or replacement).

Replacement cost: N/A — repair only.

🟡 Monitor - book inspection soon if symptoms develop.

Our recommendation:

The EGR valve is a known weak point on the OM668. Over time, soot buildup can cause the EGR valve to stick, leading to reduced power and rough running. Regular motorway driving and using high‑quality diesel can help reduce EGR clogging. If the engine warning light appears with EGR‑related codes, have the system diagnosed promptly.

Weighing Your Options?

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Mercedes A-Class 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 A-Class 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 SenseTurbocharger failure✅ Yes£600–£1,500 [PLACEHOLDER]Worth fixing — common and well‑understood repairFuel injector issues✅ Yes£300–£800 [PLACEHOLDER]Worth fixing — routine maintenance itemOil leaks (heat exchanger / pump)✅ Yes£200–£600 [PLACEHOLDER]Essential maintenance — always worth doingEGR valve failure✅ Yes£200–£500 [PLACEHOLDER]Worth fixing — straightforward repairMajor internal failure (crank, bearings)❌ Usually No£1,400–£2,800+Full engine replacement often more cost‑effective

Buying This Mercedes A-Class CDI? Check These First

Buy If

Full Mercedes service history with regular oil changes (using 5W-30 or 10W-40 fully synthetic diesel oil)
Turbocharger in good health — no whistling or smoke
Clean fuel system — no rough idle or hard starting
A well‑maintained example — the OM668 is durable when properly cared for

Avoid If

Any sign of turbocharger wear — a known weak point on the OM668
Any sign of fuel injector issues — rough running or stalling
Oil leaks from the heat exchanger or injection pump
Poor service history — the OM668 is intolerant of neglect

Closing Verdict

The Mercedes A-Class A160 and A170 CDI are powered by the OM668 1.7‑litre turbodiesel — a durable and efficient engine that was ahead of its time with common‑rail direct injection. The engine has a typical lifespan of 150,000‑155,000 miles when properly maintained. However, it has known weaknesses — turbocharger failure (rarely exceeding 130,000 km), fuel injector issues, oil leaks, and EGR valve problems. Buy on service history above all else — a well‑maintained A-Class CDI is a reliable and economical car; a neglected example can be expensive to repair.

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

→ Compare A-Class 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 A-Class CDI engine prices before you buy

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Buying Checklist

Before you buy a used Mercedes A-Class CDI (or before you commit to an engine replacement), check these:

1. Cold Start — Any smoke or rough running? (injector or glow plug warning)

2. Service History — Regular oil changes (every 8,000‑10,000 miles) — this is non‑negotiable

3. Turbo Health — Any whistling, lag, or smoke? (turbo warning)

4. Fuel System — Any hard starting, rough idle, or stalling? (injector warning)

5. Oil Leaks — Check under the vehicle and around the injection pump and heat exchanger

6. EGR System — Any engine warning lights? Any EGR‑related codes?

7. Oil Consumption — Does it use more than 1L per 1,000 miles?

8. MOT History — Check for emissions‑related failures or any advisory notes

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.

OM668.941 (DE17A)

Years1998–2001

Power60 PS (44 kW) / 160 Nm

2025 Enquiries— (pattern data)

Avg. Recon Cost£1,200–£2,000 [PLACEHOLDER]

Engine CodeYearsPower2025 EnquiriesAvg. Recon Cost

OM668.941 (DE17A)1998–200160 PS (44 kW) / 160 Nm— (pattern data)£1,200–£2,000 [PLACEHOLDER]

OM668.940 (DE17LA Red)2001–200475 PS (55 kW) / 160 Nm— (pattern data)£1,400–£2,200 [PLACEHOLDER]

OM668.940 (DE17LA)1998–200190 PS (66 kW) / 180 Nm— (pattern data)£1,600–£2,500 [PLACEHOLDER]

OM668.942 (DE17LA)2001–200495 PS (70 kW) / 180 Nm— (pattern data)£1,800–£2,800 [PLACEHOLDER]

Technical Specs

OM668 — 1.7L 4‑Cylinder Turbodiesel

Displacement1,689 cc

Cylinders4‑cylinder inline; 59° inclination

Bore x Stroke80.0 x 84.0 mm

Compression Ratio19.5:1

Fuel SystemCommon‑rail direct injection

Valves per Cylinder4

Camshaft DriveDouble roller chain

TurbochargerBorgWarner K03 with intercooler (except early A160 CDI)

Oil Capacity4.5 litres (with filter)

Recommended OilSAE 5W-30 or 10W-40 fully synthetic diesel engine oil

→ Compare A-Class CDI engine prices for your Mercedes

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Market Intelligence

Most Common Failure

Turbocharger failure — the defining weakness of the OM668

Average Enquiry Mileage

80,000

–120,000 miles

[PATTERN DATA]

Average Replacement Cost

£1,800

reconditioned, supply only

[PLACEHOLDER]

Most Requested Engine Code

OM668.940 (90 PS) — the most common A170 CDI variant

[PATTERN DATA]

Peak Enquiry Season

Autumn/Winter — cold starts expose fuel and turbo issues

[PATTERN DATA]

Regional Demand

South East20%

London14%

North West (12%) — compact car strongholds

PATTERN DATA

Regional Demand Breakdown

20%South East

14%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 A-Class CDI Owners Trust MercedesEngine.uk

Trusted A-Class CDI Engine Suppliers
every garage and engine rebuilder in our network is vetted, rated and reviewed by real A-Class owners, as part of the Engine Finders network, covering both the A160 and A170 CDI variants of the OM668 engine.
Compare A-Class CDI Engine Replacement Companies
see prices, warranty terms and supply & fit options side‑by‑side before you commit, with specialists who understand the OM668's turbocharger vulnerabilities, fuel injector issues, and the importance of regular oil changes.
UK Engine Replacement Services for the A-Class
supply‑only or full supply & fit available nationwide, covering the W168 A-Class CDI from 1998 to 2004, with specialist knowledge of Mercedes' common‑rail diesel technology.

Find the best Mercedes A-Class A160/A170 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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