Mercedes GLS400dEngine Rebuild— From £2,800
Specialist Mercedes GLS400d engine rebuilds and replacements, with registration-based engine matching, nationwide recovery and a 12-month unlimited-mileage warranty
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 GLS400d Engine
Vehicle
Mercedes GLS400d
Model
GLS
Variant
GLS400d
Fuel
Diesel MHEV
Engine
OM656 D29
Capacity
2.9L I6
Generation
X167 (2019–present)
Rebuild From
£2,800
Not sure which engine you have?
The GLS400D 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 GLS400dEngine Rebuild Price
Starting From £2,800
Engine Code
OM656 D29Rebuild From
£2,800
Generation
X167 (2019–present)
Exact price depends on condition and parts required — submit your reg for a fixed-price quote.
Mercedes GLS400d 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 GLS400D uses a completely different engine family from the V8 M178 fitted to the GLS 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 GLS400dENGINE OPTIONS
Every GLS400D is different. That's why we offer the right solution for your engine, your car and your budget.
REBUILDING YOUR GLS400D ENGINE
We rebuild the engine your GLS400D 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 GLS400D 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 GLS400D ENGINES
Restoring your existing engine to full working condition rather than replacing it outright. Our rebuild service covers this.
Learn moreREMANUFACTURED GLS400D ENGINES
Built to original specification with updated components. That's consistent with what our rebuild service delivers on the M256.
Learn moreREPLACEMENT GLS400D 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 GLS400D 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 GLS400D, 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 GLS400d rebuild looks like.
Mercedes GLS400d ENGINE REBUILD PROCESS
WHAT MERCEDES GLS400D OWNERS SAY
WE COVER YOUREXACT VEHICLE
Enter your registration below and we'll confirm your GLS400D has the M256, along with an exact rebuild price.
WHY MERCEDES GLS400D OWNERS CHOOSE US
Engine matched using VIN or registration number — confirms your GLS400d's exact spec before you're quoted
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 GLS400d
RECOVERY
Mercedes GLS 63
DIAGNOSTICS
Mercedes GLS
STRIPPED ENGINE
Mercedes GLS S
TIMING CHAIN REPLACEMENT
Mercedes GLS400d
IN FOR REBUILD
Mercedes GLS C
REBUILD IN PROGRESS
HOW IT WORKS
SEND YOURREGISTRATION
RECEIVE YOURFIXED-PRICE QUOTE
WE RECOVERYOUR CAR
REBUILD &REFIT
Most GLS 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 GLS400D 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 GLS400D ENGINE
The GLS400d is the current diesel flagship of the GLS range, fitted to the X167 generation from 2019 onwards. It uses the OM656 D29 — a 2.9-litre inline-six diesel with mild-hybrid technology, representing a step on from the older OM642 V6 diesel used in previous-generation GLS models. The OM656 is a different unit entirely from the OM642, with its own character and rebuild requirements — which is exactly why we confirm your exact engine by registration before quoting.
We continue to rebuild and replace M256 engines for every GLS400D on the road.
MERCEDES GLS400D ENGINE CODES
M256 (R190, 2023–present)
A 3.0-litre inline-six petrol mild-hybrid engine fitted to the GLS400D 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 GLS400DMERCEDES GLS400D ENGINE COMPATIBILITY
The GLS400d uses the OM656 D29 across the entire X167 generation (2019–present). Before we quote or supply anything, we confirm:
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 GLS quote — it protects you from paying for parts that don't fit your actual car.
MERCEDES GLS400D APPLICATIONS BY GENERATION
Generation
Chassis
Years
Engine Code
Fuel
MERCEDES GLS400D ENGINES BY YEAR
From the R190's launch in 2023, the GLS400D 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 GLS400D 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 GLS400D MODEL YEAR:
Mercedes GLS400d
2019 Engine Rebuild
Mercedes GLS400d
2020 Engine Rebuild
Mercedes GLS400d
2021 Engine Rebuild
Mercedes GLS400d
2022 Engine Rebuild
Mercedes GLS400d
2023 Engine Rebuild
Mercedes GLS400d
2024 Engine Rebuild
Mercedes GLS400d
2025 Engine Rebuild
Mercedes GLS400d
2026 Engine Rebuild
If your registration year isn't listed above, get in touch — we'll confirm availability directly against your reg.
MERCEDES GLS400D ENGINE COSTS
A Mercedes GLS400d 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 GLS400D ENGINE SIZES
• Mercedes GLS400d 3.0 Litre Engine (M256, I6)
MERCEDES GLS400D FUEL TYPES
• Mercedes GLS400d Petrol Mild Hybrid Engine Rebuilds
RELATED MERCEDES GLS VARIANTS
Most Mercedes GLS engine rebuilds are completed within 3-5 working days.
Nationwide recovery and collection available for all GLS models.