Mercedes GLC M274/M264/OM654 Engine SolutionsUK Specialists

A rebuilt GLC engine typically costs £2,400-£4,800 for the common 220d diesel, £2,200-£4,000 for the 300 petrol, and £7,000-£14,000 for the 63 AMG V8. Supply only - fitting adds £600-£1,200.

• GLC 220d (OM654): rebuilt unit £2,400-£4,200; used engine from £1,500
• GLC 300 (M264): rebuilt unit £2,500-£4,500; used engine from £1,800
• GLC 43 AMG (M276): rebuilt unit £4,500-£8,000; specialist fit only
• GLC 63 AMG (M177): rebuilt unit £7,000-£14,000; V8 specialist required
• Price depends on engine code, year, mileage, and supplier warranty length

The 220d's OM654 engine is fundamentally strong, but EGR cooler cracking between 40k-80k miles is the dominant failure - often requiring full engine replacement if coolant loss causes overheating.

• OM654 EGR cooler (part A6540940101) fractures from thermal stress - most searched GLC diesel fault
• AdBlue injector nozzle clogging (A0010780108) triggers countdown warnings
• NOx sensor failure causes permanent emissions lights and failed MOT
• OM651 in pre-2019 220ds suffers swirl flap actuator failure and timing chain stretch
• Well-maintained OM654 diesels regularly exceed 200,000 miles despite these issues

The OM654 diesel (2019-onwards) delivers the best long-term reliability at high mileage. For petrol buyers, the M264 has more complex 48V hybrid components to fail, while the older M274 suffers timing chain tensioner wear.

• GLC 250d with OM651 is considered "virtually indestructible" when maintained
• GLC 300 with M264 offers good reliability but BSG (48V starter-generator) can fail
• GLC 220d OM654 has one known weak point (EGR cooler) but otherwise very robust
• M274 petrol engines pre-2017 have higher timing chain failure rates
• Second-gen X254 (2022+) mild hybrids too new for long-term reliability data

A 1-3 second rattling noise on cold start is the classic warning - most common on M274 petrol engines (GLC 200/250/300, 2015-2019). Ignoring it risks engine seizure and £5,000+ repair bills.

• Cold start rattle that disappears after oil pressure builds - earliest warning sign
• Check engine light with cam/crank correlation codes (P0016/P0017)
• Metallic swarf in engine oil indicates chain guides wearing away
• Rough idle or misfire means timing has already drifted
• Preventative tensioner replacement costs £300-500 - full chain kit £1,200-1,700

Properly maintained GLC diesel engines routinely reach 250,000-300,000 miles (400,000-500,000 km) before major work. Petrol engines typically need significant attention between 120,000-180,000 miles .

• OM651 and OM654 diesels: 250,000+ miles with regular servicing
• M274/M264 petrols: 150,000-200,000 miles before major repairs likely
• OM654 EGR cooler typically fails once - after replacement, engine continues strongly
• Service interval is 10,000 miles or 12 months - use Mercedes-spec oil only
• AMG V8 engines (M276/M177) require more frequent maintenance - 120,000-150,000 miles typical

Yes, if the GLC is otherwise in good condition with no rust or major electrical faults. A rebuilt OM654 or M264 engine costs £2,500-£4,500 - far less than replacing a £18,000-£35,000 vehicle.

• GLC values remain strong - X253 (2015-2022) still worth £15,000-£30,000+
• Rebuilt engine with upgraded components (EGR cooler, timing chain tensioner) fixes original weak points
• Supply & fit typically £3,000-£6,000 depending on engine code
• New engine includes 12-month unlimited mileage warranty - peace of mind
• Only consider scrapping if body corrosion, transmission failure, or structural damage present

Mercedes-Benz specifies 229.51 or 229.52 low-SAPS oil (5W-30 or 0W-20 depending on year). Change every 10,000 miles or 12 months - stretched intervals cause timing chain wear and turbo failure .

• OM654 diesel: MB 229.52 0W-20 or 5W-30 - low-ash formula protects DPF
• M274/M264 petrol: MB 229.5 5W-30 or 0W-40 - high-spec synthetic only
• Never use non-approved oil - destroys timing chain tensioners and hydraulic lifters
• OM642 V6 diesel requires 8.5 litres of 5W-30 low-SAPS oil
• Late oil changes are the #1 cause of preventable engine failure on all GLC engines

AdBlue crystallises inside the injector nozzle (A0010780108), blocking flow and triggering countdown starters - OM654 engines (2019+) are most affected. NOx sensor failure is the second most common emissions fault.

• Crystallisation blocks the injector - ultrasonic cleaning helps but replacement often needed
• Countdown starts at 16 starts remaining - ignore and car won't restart
• NOx sensors fail due to internal heating element degradation
• Repair cost: injector £280-450, sensor replacement £350-600 each (replace both)
• Using poor-quality AdBlue or letting tank run dry accelerates injector failure

Too early for definitive long-term data, but early owner feedback suggests OM654M diesels and M254 mild hybrids are proving more reliable than first-gen facelift engines. No major systematic failures reported.

• OM654M diesel includes revised EGR cooler - fewer cracking reports so far
• Integrated starter-generator (ISG) replaces problematic belt-driven BSG from M264
• GLC 300e PHEV offers 80-mile electric range - battery health unknown long-term
• GLC 43 now uses M139l four-cylinder - reliability unproven, early AMG feedback mixed
• First major repairs expected after 100,000-150,000km - watch this space

Choose the 300e PHEV if you have home charging and mostly do sub-50 mile daily trips - 5% BIK tax saves company car drivers £3,000 annually over the 220d. Choose diesel for high-mileage motorway use where battery range won't be utilised .

• GLC 300e offers 55-80 miles electric range - covers most daily commutes
• 5% Benefit-in-Kind (BIK) tax vs 37% for diesel - huge company car saving
• Petrol PHEV cheaper to buy than diesel 300de - £3,000/year lower tax
• Real-world economy on long journeys: diesel 45-50mpg, PHEV 35-40mpg (battery depleted)
• Diesel better for towing - PHEV's extra battery weight reduces payload