Mercedes G400dEngine Rebuild— From £3,200
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Rated Mercedes Engine Specialists — 1,800+ Engines Rebuilt
Specialist technicians with 10-15 years of experience
12 Month Unlimited-Mileage Warranty
Nationwide Recovery
Free Engine Matching by Registration
M256 Specialists
Your Mercedes G400d Engine
Vehicle
Mercedes G400d
Model
G-Class
Variant
G400d
Fuel
Diesel
Engine
OM656
Capacity
2.9L I6
Generation
W463a (2018–present)
Rebuild From
£2,800
Not sure which engine you have?
The G400D uses the M256 3.0-litre inline-six mild-hybrid engine — enter your registration below and we'll confirm your exact spec before you get a quote.
DVLA & VIN verified
100% secure & private
No obligation quote
Mercedes G400dEngine Rebuild Price
Starting From £2,800
Engine Code
M256Rebuild From
£3,200
Generation
R190 (2023–present)
Exact price depends on condition and parts required — submit your reg for a fixed-price quote.
Mercedes G400d Oil Leaks & Coolant System Wear (M256 I6)
The M256 is a sophisticated 3.0-litre inline-six with an integrated starter-generator and electric auxiliary compressor — a more modern and efficient design than the older M276 V6. We replace timing chains, bearings, water pump and gaskets as standard on every M256 rebuild.
Because the G400D uses a completely different engine family from the V8 M178 fitted to the G-Class 63 and GT 63 S, parts and rebuild specifications don't cross over between them.
Source: Established M256 specialist pattern — timing chain, bearing and gasket wear across integrated-starter-generator inline-six units.
Mercedes G400dENGINE OPTIONS
Every G400D is different. That's why we offer the right solution for your engine, your car and your budget.
REBUILDING YOUR G400D ENGINE
We rebuild the engine your G400D already has instead of selling you a used engine of unknown history — strip it down, pressure-test it, and replace every worn or damaged component (timing chains, bearings, water pump, gaskets) with updated OEM parts. Near-new performance with a 12-month unlimited-mileage warranty.
From £3,200RECONDITIONED G400D ENGINES
A full strip-down, inspection and replacement of worn parts rather than a straight swap. If that's what you're after, our rebuild service is exactly that.
Learn moreREFURBISHED G400D ENGINES
Restoring your existing engine to full working condition rather than replacing it outright. Our rebuild service covers this.
Learn moreREMANUFACTURED G400D ENGINES
Built to original specification with updated components. That's consistent with what our rebuild service delivers on the M256.
Learn moreREPLACEMENT G400D ENGINES
If your existing engine is beyond economical repair, we offer complete engine replacement and fitting – sourced and fitted by our team, with the same 12-month warranty.
Learn moreUSED G400D ENGINES
Matched low-mileage used engines for when time is critical. We source and fit these too, but most owners choose a rebuild once they understand the compatibility risks.
Learn moreNOT SURE WHICH OPTION IS RIGHT FOR YOU?
Enter your registration below and we'll confirm your M256 and talk you through the best solution for your G400D, honestly.
Ask About Your Options
OUR WORKSHOP
01RECOVERY COLLECTION
02M256 ENGINE STRIPPED FOR REBUILD INSPECTION
03VALVE COVERS & COOLANT COMPONENT WORK
04TECHNICIANS AT WORK
05ENGINE TESTING (RIG)
06COMPLETED & READY FOR REFIT
Real photos from our workshop — not stock imagery. This is what a genuine Mercedes G400d rebuild looks like.
Mercedes G400d ENGINE REBUILD PROCESS
WHAT MERCEDES G400D OWNERS SAY
WE COVER YOUREXACT VEHICLE
Enter your registration below and we'll confirm your G400D has the M256, along with an exact rebuild price.
WHY MERCEDES G400D OWNERS CHOOSE US
Engine matched using VIN or registration number
Genuine specialist workshop — not a broker
Specialist technicians with 10-15 years of experience
We don't swap your engine for an unknown used unit
Nationwide recovery, workshop rebuild
12 month unlimited-mileage warranty
All engine ancillaries serviced as part of the rebuild
Trade & public enquiries welcome
Dedicated advisor from quote to fit No widely-reported engine issue for this variant — we still recommend a full inspection before any long journey.
OUR MOST RECENTMERCEDES RECOVERIES & REBUILDS
Real vehicles brought into our workshop. Open bonnets, stripped blocks, and cars ready for collection — this is what genuine engine work looks like.
Mercedes G400d
RECOVERY
Mercedes G-Class 63
DIAGNOSTICS
Mercedes G-Class
STRIPPED ENGINE
Mercedes G-Class S
TIMING CHAIN REPLACEMENT
Mercedes G400d
IN FOR REBUILD
Mercedes G-Class C
REBUILD IN PROGRESS
HOW IT WORKS
SEND YOURREGISTRATION
RECEIVE YOURFIXED-PRICE QUOTE
WE RECOVERYOUR CAR
REBUILD &REFIT
Most G-Class models are recovered within a few hours of booking. Most rebuilds are completed within 3-5 working days.
Workshop slots fill up fast — book your recovery today.
LOOKING FOR A USED ORREPLACEMENT ENGINEINSTEAD?
We supply low-mileage, VIN-matched used units too, and offer full replacement and fitting. However, most G400D owners choose a rebuild once they realise it removes compatibility risk and works out more cost-effective over the life of the car.
Enter your reg below — we'll show you every option, honestly.
ABOUT THE MERCEDES G400D ENGINE
The G400d uses the OM656 — a 2.9-litre inline-six diesel. It was fitted from 2018 across the W463a generation of the G-Class. This engine is a member of a modern family of Mercedes diesel engines also found in the S-Class and GLS. The OM656 is a reliable and powerful unit, but like all modern diesels, it benefits from regular servicing and the occasional component replacement. A full rebuild can address wear items such as timing chains, injector seals, and gaskets, restoring your engine to near-new condition.
We continue to rebuild and replace M256 engines for every G400D on the road.
MERCEDES G400D ENGINE CODES
M256 (R190, 2023–present)
A 3.0-litre inline-six petrol mild-hybrid engine fitted to the G400D from 2023 to present. The M256 features an integrated starter-generator (ISG) and electric auxiliary compressor, making it a more modern and efficient design than the older M276 V6. We replace timing chains, bearings, water pump and gaskets as standard on every M256 rebuild.
Check Your M256 G400DMERCEDES G400D ENGINE COMPATIBILITY
Because the G400d uses the OM656 engine, confirming your exact engine code is straightforward. However, we always start with your registration to ensure we match the correct specification for the W463a generation. This protects you from paying for parts that don't fit your actual vehicle.
Your exact engine code (M256) via registration or VIN
Your generation (R190)
Drivetrain and ancillary specification
Any electronics or ECU considerations specific to your exact build
This is why we always start with your registration rather than a generic G-Class quote — it protects you from paying for parts that don't fit your actual car.
MERCEDES G400D APPLICATIONS BY GENERATION
Generation
Chassis
Years
Engine Code
Fuel
MERCEDES G400D ENGINES BY YEAR
From the R190's launch in 2023, the G400D has used the M256 3.0-litre inline-six mild hybrid throughout. If you're unsure of your exact spec, we'll confirm it before you book.
The M256 has been fitted to every G400D since launch — if your registration year isn't listed above, get in touch and we'll confirm availability directly against your reg.
WE COVER EVERY MERCEDES G400D MODEL YEAR:
Mercedes G400d
2018 Engine Rebuild
Mercedes G400d
2019 Engine Rebuild
Mercedes G400d
2020 Engine Rebuild
Mercedes G400d
2021 Engine Rebuild
Mercedes G400d
2022 Engine Rebuild
Mercedes G400d
2023 Engine Rebuild
Mercedes G400d
2024 Engine Rebuild
Mercedes G400d
2025 Engine Rebuild
Mercedes G400d
2026 Engine Rebuild
If your registration year isn't listed above, get in touch — we'll confirm availability directly against your reg.
MERCEDES G400D ENGINE COSTS
A Mercedes G400d engine rebuild starts from
£2,800
A full replacement engine and fitting service is also available. Exact pricing depends on the condition of your existing engine and the parts required — submit your registration for a fixed-price quote within 30 minutes.
12 MONTH
UNLIMITED-MILEAGE
WARRANTY
MERCEDES G400D ENGINE SIZES
• Mercedes G400d 3.0 Litre Engine (M256, I6)
MERCEDES G400D FUEL TYPES
• Mercedes G400d Petrol Mild Hybrid Engine Rebuilds
RELATED MERCEDES G-CLASS VARIANTS
Most Mercedes G-Class engine rebuilds are completed within 3-5 working days.
Nationwide recovery and collection available for all G-Class models.