How much does a Mercedes GLC 300d engine replacement cost in the UK?

A reconditioned OM654 engine typically costs £5,500–£8,500 supply only, with X254 MHEV units slightly higher. A used engine costs on average £2,500–£4,500. Fitting adds £1,400–£2,000. Use our calculator for a figure specific to your GLC.

Is the Mercedes GLC 300d (OM654) engine reliable?

The OM654 is a sophisticated and powerful four‑cylinder diesel, but it has several known issues. The EGR cooler vacuum diaphragm is a common failure point causing loss of power. Timing chain tensioner wear causes cold‑start rattle — and the chain is at the back of the engine, making replacement an engine‑out job. AdBlue system failures are also common. With regular maintenance and early intervention, it can be a reliable engine.

What are the common problems with the GLC 300d engine?

EGR cooler vacuum diaphragm failure (loss of power, underboost, P0299), timing chain tensioner wear (cold‑start rattle, engine‑out repair), AdBlue system failures (NOx sensors, heaters, SCR), rocker bearing wear (ticking/popping, can lead to cam scoring), oil dilution (diesel in oil), and cooling system issues.

Is it worth replacing a GLC 300d engine, or should I scrap the car?

Depends on vehicle value and the nature of the failure. A GLC 300d is a £15,000–£35,000+ vehicle — a £6,000–£7,000 recon is 17–47% of the car's value, making replacement viable in most cases. For a timing chain failure requiring an engine‑out job (up to £3,500+), replacement may still be worthwhile. Evaluate carefully based on your car's condition and the specific repair needed.

How do I find my Mercedes GLC 300d engine code?

Listed on the VIN plate and vehicle documentation. The GLC 300d engine code is OM654 — a 2.0‑litre four‑cylinder turbo‑diesel. Tell us your registration date and we'll confirm it for free.

Can I prevent the common failures on a GLC 300d?

On the EGR cooler: if you experience loss of power or engine warning light, have the EGR system inspected immediately. On the timing chain: regular oil changes with Mercedes‑approved MB 229.51/229.52 oil and shortened intervals (5,000–8,000 miles) are essential. On the AdBlue system: use high‑quality AdBlue from reputable sources and have the system serviced regularly. At the first sign of cold‑start rattle, loss of power or AdBlue warnings, book an inspection immediately.

Mercedes GLC 300d2019–presentOM654

Mercedes GLC 300d Engine Replacement — Compare Prices & Get Quotes

The GLC 300d is powered by Mercedes' advanced OM654 2.0‑litre four‑cylinder turbo diesel — 245–288 PS and up to 550 Nm of torque across the X253 and X254 generations. Get quotes from trusted UK specialists today.

Supply & Fit Available

12-Month Warranty

Nationwide Delivery

25+ Specialists

Supply & Fit Available

12-Month Warranty

Nationwide Delivery

25+ Specialists

Mercedes GLC 300d Engines — from £2,500 to £9,500OM654

Mercedes GLC 300d Engines — from £2,500 to £9,500· OM654

Instant QuotesNo Obligation100% FreeReconditionedRebuiltUsedSupply & Fit AvailableUK-Wide Network

The GLC 300d 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?

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 GLC 300d Engine Replacement Costs

Supply Only£5,500–£8,500

Fitted (Indie)£6,800–£10,000

Warranty12–24 months

Best ForMost owners — best cost/warranty balance

Engine TypeSupply OnlyFitted (Indie)WarrantyBest For

Used Engine£2,500–£4,500£3,700–£6,0001–6 monthsBudget priority; lower‑mileage donor

Reconditioned Engine£5,500–£8,500£6,800–£10,00012–24 monthsMost owners — best cost/warranty balance

Rebuilt Engine£6,500–£9,500£7,800–£11,20012–24 monthsLong‑term ownership; 3+ year horizon

Main Dealer New£9,000–£13,000£10,500–£15,00024–36 monthsInsurance jobs, warranty claims

Figures above reflect the current OM654 generation. A replacement OM654 engine costs on average £4,500–£6,000 for a used unit, with reconditioned units significantly higher.

Labour estimate: Fitting a GLC 300d engine typically takes 14–18 hours at £65–£95/hr (independent) or £110–£160/hr (London/SE dealer). The OM654’s timing chain is at the back of the engine, making many repairs engine‑out jobs.

→ Compare GLC 300d engine prices from UK specialists

Common Problems

1. EGR Cooler Vacuum Diaphragm Failure (OM654 — All Years)

Symptoms: Loss of power, underboost (P0299 code), engine warning light, rough running, white smoke from exhaust, coolant loss.

Typical mileage: 30,000–70,000 miles

Repair cost: £600–£1,500 (EGR cooler replacement, vacuum diaphragm)【PLACEHOLDER — confirm vs cost sheet】

Replacement cost: N/A — repair only (if caught before overheating)

🟠 Check - book inspection urgently if you experience loss of power or engine warning light

Our recommendation:

The OM654’s EGR cooler vacuum diaphragm is a common failure point. The diaphragm can fail repeatedly, causing vacuum leaks, underboost and loss of power. If you experience loss of power or an engine warning light, have the EGR system inspected. Carbon buildup and corrosion are also common causes of EGR cooler failure. Catching it early prevents more serious engine damage.

1. EGR Cooler Vacuum Diaphragm Failure (OM654 — All Years)

Symptoms: Loss of power, underboost (P0299 code), engine warning light, rough running, white smoke from exhaust, coolant loss.

Typical mileage: 30,000–70,000 miles

Repair cost: £600–£1,500 (EGR cooler replacement, vacuum diaphragm)【PLACEHOLDER — confirm vs cost sheet】

Replacement cost: N/A — repair only (if caught before overheating)

🟠 Check - book inspection urgently if you experience loss of power or engine warning light

Our recommendation:

2. Timing Chain Tensioner Wear (OM654 — All Years)

Symptoms: Rattling noise on cold start (lasting a few seconds), metallic ticking, engine warning light with timing‑related fault codes.

Typical mileage: 40,000–80,000 miles

Repair cost: £1,500–£3,500 (tensioners, chain guides and chain replacement)【PLACEHOLDER — confirm vs cost sheet】

Replacement cost: £5,500–£9,500 (full engine replacement if chain snaps)

🔴 Immediate - if you hear rattle, book an inspection today

Our recommendation:

The OM654’s timing chain is mounted at the back of the engine, making replacement an engine‑out job. If the chain snaps, there is a risk of sudden loss of propulsion and severe engine damage. Regular oil changes with Mercedes‑approved oil (MB 229.51/229.52) are essential. At the first sign of cold‑start rattle, have the timing chain system inspected immediately.

3. AdBlue System Failures (OM654 — All Years)

Symptoms: Check engine light, AdBlue warning, reduced power, countdown to start restriction (usually 500 miles), engine warning light.

Typical mileage: 30,000–80,000 miles

Repair cost: £500–£2,500 (sensor replacement, AdBlue heater, SCR system repair)【PLACEHOLDER — confirm vs cost sheet】

Replacement cost: N/A — repair only

🟠 Check - book inspection urgently if AdBlue countdown appears

Our recommendation:

The AdBlue (SCR) system on the OM654 is a common failure point. Faults include NOx sensors, level sensors, heaters and the dosing unit. If the AdBlue system fails and the countdown reaches zero, the car will not start. Use high‑quality AdBlue from reputable sources and have the system serviced regularly. At the first sign of an AdBlue warning, book an inspection immediately.

Ready to Compare?

Get Matched With a Vetted Mercedes Specialist

25+ vetted Mercedes specialists, every GLC 300d engine covered, with a 12‑month warranty as standard.

Get My Free GLC 300d Engine Quotes Now

GLC 300d — 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.

GLC 300d — 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 SenseEGR cooler vacuum diaphragm failure✅ Yes£600–£1,500Replace diaphragm or cooler — catch it earlyTiming chain tensioner wear✅ Yes£1,500–£3,500Engine‑out job — catch it early before chain snapsAdBlue system failure✅ Yes£500–£2,500Sensor or heater replacement — use quality AdBlueRocker bearing wear✅ Yes£1,000–£2,500Catch it early — before cam lobes are scoredSevere engine damage (chain snap / overheating)❌ Usually NoEngine replacementLittle left to salvage — replacement is the only option

Buying This GLC 300d? Check These First

Buy If

No cold‑start rattle — timing chain tensioner in good condition
No loss of power or engine warning light — EGR cooler in good condition
AdBlue system serviced — quality AdBlue used
Full Mercedes service history with MB‑spec oil (MB 229.51/229.52)

Avoid If

Cold‑start rattle with no tensioner history — timing chain may be failing — walk away
Loss of power with no diagnosis — EGR cooler may be failing
AdBlue warning light with no diagnosis — potential SCR system failure
Poor service history — OM654 engines are sensitive to neglect

Closing Verdict

The OM654 is Mercedes’ most advanced four‑cylinder diesel — smooth, powerful and efficient. But it has several well‑documented weaknesses: the EGR cooler vacuum diaphragm (loss of power), timing chain tensioner wear (cold‑start rattle — engine‑out job), rocker bearing wear and AdBlue system failures. Buy on full service history, listen for cold‑start rattle and check for AdBlue warnings. A well‑maintained GLC 300d is a rewarding, long‑lived SUV; a neglected one is a £7,000+ bill waiting to happen.

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

→ Compare GLC 300d 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 GLC 300d 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 GLC 300d (or before you commit to an engine replacement), check these:

Cold Start — Listen for rattling; timing chain tensioner indicator

Loss of Power — Check for underboost; EGR cooler vacuum diaphragm indicator

AdBlue System — Check for warning lights — AdBlue system failure indicator

Service History — including engine era (OM654) and confirmed oil‑change intervals (MB 229.51/229.52)

Oil Level — Check for over‑ or under‑filling; oil dilution is a known concern

Coolant Level — Check for unexplained loss; EGR cooler or cooling system issues

Turbo Health — Listen for whistling or whining; turbo actuator issues possible

MOT History — Check for emissions‑related failures (AdBlue/SCR)

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.

OM654 (2.0 4‑cyl turbo diesel)

Years2019–2022

Power245 PS (180 kW) @ 4,200 rpm; 500 Nm @ 1,600–1,800 rpm

2025 Enquiries— (pattern data)

Avg. Recon Cost£5,500–£8,500【PLACEHOLDER】

Engine CodeYearsPower2025 EnquiriesAvg. Recon Cost

OM654 (2.0 4‑cyl turbo diesel)2019–2022245 PS (180 kW) @ 4,200 rpm; 500 Nm @ 1,600–1,800 rpm— (pattern data)£5,500–£8,500【PLACEHOLDER】

OM654 (2.0 4‑cyl turbo diesel, MHEV)2022–present269–288 PS (215 kW) @ ~4,000 rpm; 550 Nm @ 1,800 rpm— (pattern data)£6,000–£9,500【PLACEHOLDER】

Technical Specs

OM654 2.0 4‑cyl diesel

Displacement1,950 cc

Cylinders4‑cylinder inline

Compression Ratio15.5:1 (approx.)

Fuel SystemCommon‑rail direct injection

TurbochargerTwo‑stage turbocharger (sequential)

ValvetrainDOHC with 4 valves per cylinder

→ Compare GLC 300d engine prices for your Mercedes

Get quotes from trusted UK specialists in minutes.

Market Intelligence

Most Common Failure

EGR cooler vacuum diaphragm failure — the most frequently reported OM654 issue

Average Enquiry Mileage

40,000

–60,000 miles【PATTERN DATA】

Average Replacement Cost

£6,500

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

Most Requested Engine Code

OM654【PATTERN DATA】

Peak Enquiry Season

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

Regional Demand

South East19%

London17%

South West (14%)【PATTERN DATA】

Regional Demand Breakdown

19%South East

17%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.

Find the best Mercedes GLC 300d engine replacement UK drivers rely on. Compare prices from trusted specialists on EnginesMarket today and get back on the road with confidence — from £2,500 for a used unit to £9,500 for a fully rebuilt diesel.

Compare Mercedes GLC 300d 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