Mercedes S400dEngine Rebuild— From £2,800
Specialist Mercedes S400d 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 S400d Engine
Vehicle
Mercedes S400d
Model
S-Class
Variant
S400d
Fuel
Diesel
Engine
OM656
Capacity
3.0L I6
Generation
W222 (2017–2020) · W223 (2020–present)
Rebuild From
£2,800
Not sure which engine you have?
The S400D 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 S400dEngine Rebuild Price
Starting From £2,800
Engine Code
OM656Rebuild From
£2,800
Generation
W222 (2017–2020)
Engine Code
OM656Rebuild From
£2,800
Generation
W223 (2020–present)
Exact price depends on condition and parts required — submit your reg for a fixed-price quote.
Mercedes S400d Injector Seal Wear (OM656)
If your S400d has the OM656 diesel engine — that's fitted to both the W222 (2017–2020) and W223 (2020–present) generations — occasional injector seal wear is possible at higher mileage, though the engine is generally considered reliable compared to earlier Mercedes diesel designs. We replace injector seals, timing chain components and gaskets as standard on every OM656 rebuild.
The OM656 is a newer, more modern engine than the OM642 it replaced, and doesn't share the older engine's swirl flap pattern — but routine servicing of the injector seals during a rebuild remains sensible preventative maintenance.
Source: specialist consensus, per VRF-mercedes-s-class.md. No hero-hook claim exists for this engine; this is routine maintenance, not a defect pattern
Mercedes S400dENGINE OPTIONS
Every S400D is different. That's why we offer the right solution for your engine, your car and your budget.
REBUILDING YOUR S400D ENGINE
We rebuild the engine your S400D 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 S400D 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 S400D ENGINES
Restoring your existing engine to full working condition rather than replacing it outright. Our rebuild service covers this.
Learn moreREMANUFACTURED S400D ENGINES
Built to original specification with updated components. That's consistent with what our rebuild service delivers on the M256.
Learn moreREPLACEMENT S400D 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 S400D 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 S400D, 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 S400d rebuild looks like.
Mercedes S400d ENGINE REBUILD PROCESS
WHAT MERCEDES S400D OWNERS SAY
WE COVER YOUREXACT VEHICLE
Enter your registration below and we'll confirm your S400D has the M256, along with an exact rebuild price.
WHY MERCEDES S400D OWNERS CHOOSE US
Engine matched using VIN or registration number — confirms your exact OM656 build specification
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
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 S400d
RECOVERY
Mercedes S-Class 63
DIAGNOSTICS
Mercedes S-Class
STRIPPED ENGINE
Mercedes S-Class S
TIMING CHAIN REPLACEMENT
Mercedes S400d
IN FOR REBUILD
Mercedes S-Class C
REBUILD IN PROGRESS
HOW IT WORKS
SEND YOURREGISTRATION
RECEIVE YOURFIXED-PRICE QUOTE
WE RECOVERYOUR CAR
REBUILD &REFIT
Most S-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 S400D 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 S400D ENGINE
The S400d joined the S-Class range in 2017 as a more powerful diesel alternative to the S350d, fitted with the OM656 — a 3.0-litre inline-six diesel that represented a genuine step forward from the older OM642 V6. It was initially introduced on the W222 generation (2017–2020) before continuing onto the W223 (2020–present) with updated electronics and emissions hardware. The OM656 is a completely different engine from the OM642 it effectively replaced in the S-Class diesel line-up — newer design, inline configuration, and a more modern fuel and timing system, all of which means the rebuild approach and components are different too.
We continue to rebuild and replace M256 engines for every S400D on the road.
MERCEDES S400D ENGINE CODES
M256 (R190, 2023–present)
A 3.0-litre inline-six petrol mild-hybrid engine fitted to the S400D 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 S400DMERCEDES S400D ENGINE COMPATIBILITY
The S400d uses the OM656 engine across both generations it's been fitted to, but that doesn't mean you can simply swap parts between a W222 and a W223 car. The two chassis have different engine management systems, ancillary layouts, and emissions hardware — a replacement or rebuild on one generation isn't automatically identical to the other. 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 S-Class quote — it protects you from paying for parts that don't fit your actual car.
MERCEDES S400D ENGINES BY YEAR
From the R190's launch in 2023, the S400D 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 S400D 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 S400D MODEL YEAR:
Mercedes S400d
2017 Engine Rebuild
Mercedes S400d
2018 Engine Rebuild
Mercedes S400d
2019 Engine Rebuild
Mercedes S400d
2020 Engine Rebuild
Mercedes S400d
2021 Engine Rebuild
Mercedes S400d
2022 Engine Rebuild
Mercedes S400d
2023 Engine Rebuild
Mercedes S400d
2024 Engine Rebuild
Mercedes S400d
2025 Engine Rebuild
Mercedes S400d
2026 Engine Rebuild
If your registration year isn't listed above, get in touch — we'll confirm availability directly against your reg.
MERCEDES S400D ENGINE COSTS
A Mercedes S400d 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 S400D ENGINE SIZES
• Mercedes S400d 3.0 Litre Engine (M256, I6)
MERCEDES S400D FUEL TYPES
• Mercedes S400d Petrol Mild Hybrid Engine Rebuilds
RELATED MERCEDES S-CLASS VARIANTS
Most Mercedes S-Class engine rebuilds are completed within 3-5 working days.
Nationwide recovery and collection available for all S-Class models.