Is the Mercedes-Benz GLK 320 / 350 CDI engine reliable?

The OM642 V6 diesel is considered a 'model of reliability' and is 'very stoutly built'. However, it has well-documented weaknesses: oil cooler seal failure (a design flaw), timing chain stretch (especially on 2012–2015 models), and swirl flap motor failure. With these addressed, the engine is capable of high mileage.

What are the common problems with the Mercedes-Benz GLK 320 and 350 CDI?

Oil cooler seal failure (the most infamous OM642 issue — requires 9+ hours of labour), timing chain stretch (rattling on cold start), swirl flap motor failure (P2015 code, loss of low-end torque), EGR valve clogging, and turbocharger actuator issues. The oil cooler seals and timing chain are the most critical concerns.

Is it worth replacing a Mercedes-Benz GLK 320/350 CDI engine, or should I scrap the car?

GLK values range from £5,000–£15,000 depending on condition and spec. A £2,500–£6,000 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 GLK 320 or 350 CDI engine code?

Listed on the VIN plate and vehicle documentation. GLK 320 CDI (2008–2010) uses OM642.961; GLK 350 CDI (2010–2012) uses OM642.832; GLK 350 CDI BlueEFFICIENCY (2012–2015) uses OM642.835. Tell us your registration date and we'll confirm it for free.

Can I repair the OM642 oil cooler seals, or does the engine need replacement?

The oil cooler seals can be replaced — they are wear items. Replacement costs £600–£1,500 and takes approximately nine hours of labour. The seals are located deep within the 'V' of the engine, requiring removal of numerous ancillary parts. If the seals fail and cause oil starvation, the engine can be destroyed. A preventative seal replacement with updated Viton seals is far cheaper than a full engine replacement (£2,500+). At the first sign of an oily mess under the engine, book an inspection immediately.

Mercedes-Benz GLK 320/350 CDI2008–2015OM642 V6 Diesel

Mercedes-Benz GLK 320 CDI / 350 CDI Engine Replacement — Compare Prices & Get Quotes

Name: Mercedes-Benz GLK 320/350 CDI UK Engine Enquiry Data 2025
Creator: MercedesEngine.uk

The GLK 320 CDI and 350 CDI are powered by Mercedes' OM642 3.0-litre V6 diesel — a smooth, torquey engine that's a "model of reliability", but one with well-documented weaknesses: oil cooler seals, timing chain stretch and swirl flap motor failure are all costly to address. Get quotes from UK specialists for reconditioned, rebuilt and used units today.

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Mercedes-Benz GLK 320/350 CDI Engines — from £1,200 to £6,000Code: OM642

Mercedes-Benz GLK 320/350 CDI Engines — from £1,200 to £6,000· Code: OM642

Instant QuotesNo Obligation100% FreeReconditionedRebuiltUsedSupply & Fit AvailableUK-Wide Network

The GLK 320/350 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 GLK 320/350 CDI Engine Replacement Costs

Supply Only£2,500–£4,500

Fitted (Indie)£4,500–£6,500

Warranty12–24 months

Best ForMost owners — best cost/warranty balance

Engine TypeSupply OnlyFitted (Indie)WarrantyBest For

Used Engine£1,200–£2,500£2,500–£4,5001–6 monthsBudget priority; older OM642.961 examples

Reconditioned Engine£2,500–£4,500£4,500–£6,50012–24 monthsMost owners — best cost/warranty balance

Rebuilt Engine£4,000–£6,000£6,000–£8,50012–24 monthsLong‑term ownership; 3+ year horizon

Main Dealer New£6,000–£9,000+£8,000–£11,000+24–36 monthsInsurance jobs, warranty claims

Figures above reflect the current GLK CDI market. OM642 engines are relatively common and parts are available, but labour costs for repairs like oil cooler seals (9+ hours) can be significant. Used engines for the GLK 320 CDI (OM642.961) are more readily available than the rarer 350 CDI BlueEFFICIENCY (OM642.835).

Labour estimate: Fitting a GLK CDI engine typically takes 12–16 hours at £65–£95/hr (independent) or £110–£160/hr (London/SE dealer). The longitudinal V6 layout makes access reasonable, but the oil cooler location in the "V" of the engine adds complexity.

→ Compare GLK CDI engine prices from UK specialists

Common Problems

1. Oil Cooler Seal Failure (All OM642 Variants) — "The Infamous Oil Leak"

Symptoms: Oil spots under the car, burning oil smell, visible oil residue on the engine block, low oil level warning, oily mess under the engine bay

Typical mileage: 60,000–120,000 miles

Repair cost: £600–£1,500 (oil cooler seal replacement — approximately 9 hours labour)

Replacement cost: £2,500–£4,500 (if oil starvation causes engine damage)

🟠 Check - book inspection urgently

Our recommendation:

The OM642's oil cooler seals are the most infamous weak point on this engine. The oil cooler sits within the "V" of the engine, beneath a host of ancillary parts. A "design flaw from Mercedes" means the original seals degrade over time. The updated Viton (purple) seals are an improvement, but even these can fail before 100,000 miles. Replacing two small o-rings requires approximately nine hours of labour — but it's far cheaper than a new engine. If you see an "oily mess all over the engine", book this job immediately.

Read the full oil cooler seal failure guide

1. Oil Cooler Seal Failure (All OM642 Variants) — "The Infamous Oil Leak"

Symptoms: Oil spots under the car, burning oil smell, visible oil residue on the engine block, low oil level warning, oily mess under the engine bay

Typical mileage: 60,000–120,000 miles

Repair cost: £600–£1,500 (oil cooler seal replacement — approximately 9 hours labour)

Replacement cost: £2,500–£4,500 (if oil starvation causes engine damage)

🟠 Check - book inspection urgently

Our recommendation:

Read the full oil cooler seal failure guide

2. Timing Chain Stretch (All OM642 Variants — Especially 2012–2015)

Symptoms: Rattling or slapping noise from the front of the engine, lasting 2–5 seconds after cold start, metallic ticking, engine warning light

Typical mileage: 60,000–120,000 miles

Repair cost: £1,500–£3,500 (timing chain, tensioner and guide replacement)

Replacement cost: £2,500–£4,500 (if chain jumps and causes valve interference)

🔴 Immediate - a stretched timing chain can cause catastrophic engine failure

Our recommendation:

Timing chain stretch is a serious issue on the OM642. The chain tensioner has small notches that act as stops; when the chain stretches, the piston pushes past these stops. Owners have reported chain stretch as early as 54,600 miles. The 2008–2013 models are considered "bad years" for timing chain issues. If you hear rattling on cold start, book an inspection immediately — a preventative chain replacement is far cheaper than a full engine rebuild. The 2012–2015 BlueEFFICIENCY models appear to be particularly susceptible.

Read the full timing chain failure guide

3. Swirl Flap Motor Failure (All OM642 Variants)

Symptoms: Engine warning light, loss of low-end torque, hesitation on acceleration, increased emissions, irregular idle speed

Typical mileage: 60,000–120,000 miles

Repair cost: £500–£1,200 (swirl flap motor replacement)

Replacement cost: N/A — repair only

🟡 Monitor - book inspection soon

Our recommendation:

The swirl flap motor on the OM642 can fail due to oil ingress through the air hose. Carbon build-up can also cause the flaps to stick. Some owners use a bypass resistor to fix the P2015 trouble code, but the proper repair is replacing the motor and cleaning the intake manifold. While the motor itself is not expensive, the labour adds up. If you see an engine warning light or experience hesitation, have the swirl flap system inspected.

Read the full swirl flap motor failure guide

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GLK 320/350 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.

GLK 320/350 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 failure✅ Yes£600–£1,500Labour-intensive (9+ hours) but cheaper than a new engineTiming chain stretch✅ Yes£1,500–£3,500Labour-intensive but far cheaper than a full engine replacementTiming chain failure (engine damage)❌ Usually NoEngine replacementIf chain jumps and valves hit pistons, replacement is the only optionSwirl flap motor failure✅ Yes£500–£1,200Well-understood repair — bypass resistor is a cheap alternativeEGR valve clogging✅ Yes£300–£800Cleaning or replacement — restore smooth runningTurbocharger actuator failure✅ Yes£500–£1,500Replacement or cleaning — catch before turbo damage

Buying This GLK 320/350 CDI? Check These First

Buy If

Evidence of oil cooler seal replacement (preferably with updated Viton seals) — the defining OM642 issue addressed
No rattling on cold start — timing chain should be healthy
Full service history with regular oil changes (every 10,000 miles) — the OM642 rewards good maintenance
Post-2010 GLK 350 CDI with documented timing chain inspection
Evidence of swirl flap motor replacement or EGR cleaning

Avoid If

Any rattling on cold start — timing chain stretch is likely
Oily mess under the engine — oil cooler seals are failing
2012–2015 BlueEFFICIENCY with no proof of timing chain work — these models are more susceptible
Engine warning light without a clear diagnosis — swirl flap or EGR issues are expensive
Poor service history — the OM642 is robust but unforgiving of neglect

Closing Verdict

The OM642 V6 diesel is generally a reliable engine, but it has three well-known weaknesses: oil cooler seals (a design flaw), timing chain stretch (especially on later models), and swirl flap motor failure. The oil cooler seal replacement is the most common — and the most labour-intensive — job on the OM642. With diligent maintenance and these issues addressed, the GLK CDI will reward you with smooth, effortless torque and impressive longevity. Buy on history, maintain on schedule, and the OM642 will serve you well.

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

→ Compare GLK CDI engine prices before you buy

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Buying Checklist

Before you buy a used Mercedes-Benz GLK 320 or 350 CDI (or before you commit to an engine replacement), check these:

1. Cold Start — Listen for rattling or slapping lasting 2–5 seconds (timing chain stretch warning — the most critical check on the OM642)

2. Oil Leaks — Any oily mess under the engine bay? (oil cooler seal failure)

3. Service History — including which generation (320 CDI, 350 CDI or 350 CDI BlueEFFICIENCY) and evidence of major maintenance

4. Oil Cooler Seal History — Has the updated Viton seal been fitted?

5. Timing Chain History — Has the chain been inspected or replaced? (especially important on 2012–2015 models)

6. Engine Warning Light — Have codes been read? (P2015 indicates swirl flap issues)

7. Performance — Any hesitation or loss of low-end torque? (swirl flap motor or EGR issues)

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

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 — three OM642 variants across the GLK CDI's production run.

OM642.961

Years2008–2010

Power224 hp / 540 Nm

2025 Enquiries[PATTERN DATA]

Avg. Recon Cost£2,500–£4,500 [MB-QUOTE]

Engine CodeYearsPower2025 EnquiriesAvg. Recon Cost

OM642.9612008–2010224 hp / 540 Nm[PATTERN DATA]£2,500–£4,500 [MB-QUOTE]

OM642.8322010–2012231 hp / 540 Nm[PATTERN DATA]£2,800–£5,000 [MB-QUOTE]

OM642.8352012–2015265 hp / 620 Nm[PATTERN DATA]£3,000–£6,000 [MB-QUOTE]

Technical Specs

OM642.835 — GLK 350 CDI BlueEFFICIENCY

Displacement2,987cc (3.0‑litre)

CylindersV6, 72° configuration

Bore x Stroke83.0 mm x 92.0 mm

Compression Ratio15.5:1

Fuel SystemCommon-rail direct injection

Camshaft DriveDuplex roller chain

Oil Capacity8.0 litres (with filter)

TurbochargerVariable geometry turbocharger with intercooler

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Market Intelligence

Most Common Failure

Oil cooler seal failure — the defining OM642 issue; a design flaw requiring 9+ hours of labour

Average Enquiry Mileage

70,000

–120,000 miles【PATTERN DATA】

Average Replacement Cost

£2,500

–£6,000 reconditioned, supply only depending on variant【MB-QUOTE】

Most Requested Engine Code

OM642.961 — the original GLK 320 CDI【PATTERN DATA】

Peak Enquiry Season

Autumn — pre‑winter vehicle preparation【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 GLK CDI Engine Suppliers
every garage and engine rebuilder in our network is vetted, rated and reviewed by real GLK 320 and 350 CDI owners, as part of the Engine Finders network, across all three OM642 variants — no matter which GLK diesel era you drive.
Compare GLK CDI Engine Replacement Companies
see prices, warranty terms and supply & fit options side‑by‑side before you commit, with specialists who genuinely understand the OM642's oil cooler seals, timing chain, and swirl flap motor nuances.
UK Engine Replacement Services for GLK 320/350 CDI
supply‑only or full supply & fit available nationwide, covering Mercedes' compact luxury diesel SUV with a 12‑month warranty as standard.

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