Mercedes B Class M270/OM651/M282 Engine SolutionsUK Specialists

A rebuilt Mercedes-Benz B Class engine typically costs £1,500-£3,500 supply-only, depending on engine code (OM651, OM654, M270) and generation. W245 diesels are cheapest; OM654 units for W247 command premium pricing.

• OM651.901 (B180/B200 CDI W246): £1,800-£2,800 rebuilt
• OM654.920 (B180d/B200d W247): £1,900-£3,500 rebuilt
• M270.910 (B160/B180 petrol W246): £1,200-£2,400 rebuilt
• Used engines from breakers: £900-£1,800 depending on mileage
• Fitting adds £400-£800 at a specialist (not dealer)

The B200 CDI with OM640 (W245, 2005-2011) and facelift OM651 (W246, 2014-2018) are considered highly reliable, often exceeding 200,000 miles. However, OM651 timing chains and OM654 AdBlue systems have documented weak points.

• B200 CDI (2008-2012 facelift) called "gold standard reliability" by specialists
• OM651 timing chain tensioner recalls affected Feb-Nov 2014 builds
• OM654 AdBlue pump and NOx sensor failures common from 30k miles
• W245 CDI engines regularly reach 217,000-280,000 miles with maintenance
• OM607 1.5-litre diesel subject to 2017-2018 emissions software updates

OM651 diesel timing chain failure (W246, 60k-100k miles) and M270 petrol camshaft wear (W246, 50k-90k miles) dominate replacement enquiries. OM654 AdBlue system faults affect newer W247 diesels from 30,000 miles.

• OM651: timing chain tensioner failure, injector seal leaks, EGR cooler cracking
• M270 petrol: camshaft bearing wear, timing chain stretch, HPFP failure
• OM654: AdBlue pump, NOx sensor, SDPF degradation
• OM640 (W245 diesel): turbo bearing wear, injector failure around 120k miles
• P0016 error code indicates camshaft/crankshaft correlation (timing chain stretch)

Avoid early W245 petrol compressors (2005-2008 B200 Turbo) due to supercharger clutch and oil consumption issues. Also be cautious with 2011-2013 OM651 diesels before timing chain tensioner recalls and early 2019 OM654 units with AdBlue teething problems.

• B200 Turbo (W245 pre-2008): supercharger magnetic clutch failure, heavy oil use
• Early OM651 (2011-2013): higher timing chain failure risk before recall improvements
• 7G-DCT gearbox on 2011-2013 W246: erratic shifts, repair costs up to £3,500
• Early W247 OM654 (2019): AdBlue system bugs requiring multiple software updates
• CVT transmission on early W245: complete failure at £4,000-£5,000 repair cost

Well-maintained OM651 and OM640 diesels regularly reach 200,000-280,000 miles. M270 petrol engines typically last 150,000-180,000 miles with proper servicing. OM654 diesels are too new for definitive data but expected to match OM651 longevity.

• OM640/W245 CDI: 217,000-280,000 miles with regular maintenance
• OM651: 180,000-250,000 miles if timing chain addressed preventatively
• M270 petrol: 150,000-180,000 miles; camshaft wear the main limiter
• Facelift (2008+) engines significantly more durable than early units
• Short-trip driving kills DPF on diesels - use for longer journeys

OM651 and M270 engines suffer timing chain tensioner failure (diesel) or chain stretch (petrol). Specialist preventative replacement costs £900-£1,400. Full engine replacement after chain snap costs £2,800-£4,200 fitted.

• OM651: tensioner loses hydraulic pressure, chain rattles on cold start
• M270: chain stretch and camshaft adjuster wear cause rattle
• Preventative chain replacement: £900-£1,400 at specialist
• After valve damage: £2,200-£3,200 for head rebuild
• Complete rebuilt engine: £2,800-£4,200 fitted with warranty

Diesel engines (OM640, OM651) outlast petrols by 50,000-100,000 miles but have higher repair costs when they fail. Petrol M270 units are cheaper to rebuild but suffer camshaft wear earlier. Choose diesel for high mileage, petrol for urban use.

• Diesel: 200k-280k miles possible but timing chain risk
• Petrol: 150k-180k miles typical; camshaft wear from 50k miles
• Diesel repairs (injectors, DPF, turbo) more expensive than petrol
• OM654 diesel AdBlue faults make petrol simpler for low-mileage owners
• B200 CDI (136hp facelift) widely considered most reliable variant

OM654 diesel engines (W247 B180d/B200d, 2019+) suffer AdBlue pump, injector, and NOx sensor failures. Crystallisation blocks the dosing valves, triggering countdown mode with limited starts. Specialist repair costs £350-£1,400; ignoring it can require full engine replacement.

• Two-stage AdBlue system (motors near SCR + underbody SCR) doubles failure points
• Crystallisation clogs dosing valves - XENTRY diagnostics required
• Single component replacement: £350-£600 at specialist
• Full AdBlue system overhaul: £900-£1,400
• Without repair, countdown leads to immobilised car and potential engine damage

For W245 models worth £1,500-£3,500, a £2,400-£3,400 rebuilt engine often exceeds the car's value. However, if the body and transmission are sound, specialist replacement with 12-month warranty can be cheaper than replacing the whole vehicle. W246 and W247 models (worth £5k-£15k) are almost always worth repairing.

• W245 (2005-2011): value £1.5k-£3.5k - borderline economical
• W246 (2011-2018): value £4k-£10k - replacement makes sense
• W247 (2019+): value £10k-£18k - definitely worth replacing
• Rebuilt engine (£2.4k-£4.2k fitted) cheaper than comparable replacement car
• Factory-quality rebuild with upgraded components often outlasts original

Check your vehicle's service booklet, door pillar sticker, or V5C logbook for the six-digit engine code (e.g., OM651.901). Enter your registration on EngineMarket above - we instantly identify your exact engine, variant, and compatible replacement options.

• Engine code format: three letters + three numbers (OM651.901, M270.910)
• Found on driver's side door pillar sticker or V5C section 4
• W245 (2005-2011): OM640 (diesel) or M266 (petrol)
• W246 (2011-2018): OM607/OM651 (diesel) or M270 (petrol)
• W247 (2019+): OM654 (diesel) or M282 (petrol/MHEV/PHEV)