Jimmy
“Thanks to EngineMarket, I saved over £1,200 on my engine replacement and got matched with a great local specialist within the hour.”
Get quotes today from trusted UK Mercedes Benz G Class engine specialists. Compare prices on reconditioned, rebuilt and used engines - supply & fit available nationwide.
-> Rebuilt units from £4,995 · Common codes: OM642.DE30.LA, OM642.LS, OM656, OM603
-> Rebuilt units from £5,500 · Common codes: M176, M177, M113, M117
-> Rebuilt units from £7,500 · Common codes: M157, M177 (G63), M279 (G65)
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Get Instant Quotes from Mercedes - Benz Engine Specialists Across the UK - 100% free, no obligation. Most replacements completed within 3-5 days.
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The table below shows typical UK rebuilt engine replacement costs across different Mercedes Benz G Class variants, covering known failure causes, engine codes, fuel types and engine sizes.

Customer Reviews
Rated 4.8 out of 5 by 1,081 verified customers who sourced reconditioned and used Mercedes Benz G Class engines through EngineMarket.
Jimmy
“Thanks to EngineMarket, I saved over £1,200 on my engine replacement and got matched with a great local specialist within the hour.”
Pete
“Got three quotes within an hour and chose the best deal easily. The whole process was quick, clear and stress-free.”
Sophie
“I wasn't sure what I needed, but they helped me identify the right engine and connected me with a trusted garage.”
Thanks to EngineMarket, I saved over £1,200 on my engine replacement and got matched with a great local specialist within the hour.”
- Jimmy, London
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From the rugged G 350 d to the ferocious G 63 AMG, our network of UK Mercedes Benz G Class engine specialists helps you compare rebuilt, reconditioned and used engine prices. Typical range for a rebuilt unit with 24-month warranty is £4,500-£25,000 - supply & fit available nationwide.
Diesel Variants
Petrol Variants
Performance Variants
Every engine code fitted to the Mercedes Benz G Class across all generations, with technical specs, compatible variants and trims, known failure points, and average rebuilt prices from UK specialists. Select any engine code to compare quotes.
Extracted from detailed diesel engine families across Mercedes Benz G Class variants.
Extracted from detailed petrol and performance engine families across Mercedes Benz G Class variants.
Every rebuilt engine includes a minimum 12-month unlimited mileage warranty.
Why G Class Diesel Engines Leak Oil Excessively
Mercedes Benz G Class G 320 CDI, G 350 CDI, G 350 d (2006-2023, OM642 DE30 LA & OM642 LS)
60,000 - 90,000 miles
| Repair Tier | Dealer Price | Specialist Price | What It Involves | Longevity / Suitability |
|---|---|---|---|---|
Minor - Seal Replacement Minor | £1,800 - £2,500 | £900 - £1,400 | Replace oil cooler seals (A6421800003 revised part), flush cooling system, new oil and filter | 60k-80k miles if using revised Viton seals |
Intermediate - Oil Cooler & Seal Assembly Intermediate | £2,500 - £3,500 | £1,400 - £2,000 | Replace complete oil cooler unit with revised seals, coolant flush, thermostat inspection | 80k-100k miles; recommended if cooler shows corrosion |
Full Replacement - Rebuilt Engine Best Value | £7,500 - £10,000 | £4,800 - £7,500 | Supply & fit rebuilt OM642 with upgraded seals, new oil pump chain, turbo inspected | 100k+ miles with extended warranty cover |
If caught early with only external weeping, the seal-only specialist fix at £900-£1,400 is excellent value and should last 60k+ miles with revised seals. However, if the leak has caused coolant contamination or the engine has overheated, we recommend the full rebuilt route - contaminated oil galleries often cause turbo or bearing failure within 10k-15k miles of a partial repair.
A failed engine doesn't have to mean the end of your G Class. Whether you're dealing with an OM642 oil leak, an AMG turbo actuator failure, or a classic OM603 timing chain issue, EnginesMarket makes it simple to compare prices from trusted UK Mercedes Benz G Class specialists. Every rebuilt engine in our network includes upgraded components designed to address the original failure point, a minimum 12-month unlimited mileage warranty, and nationwide delivery with supply & fit options available.
Compare Mercedes Benz G Class Engine Replacement Prices Now →Mercedes Benz G Class G 320 CDI, G 350 CDI, G 350 d (2006-2023, OM642 DE30 LA & OM642 LS)
60,000 - 90,000 miles
Replace oil cooler seals (A6421800003 revised part), flush cooling system, new oil and filter
Replace complete oil cooler unit with revised seals, coolant flush, thermostat inspection
Supply & fit rebuilt OM642 with upgraded seals, new oil pump chain, turbo inspected
If caught early with only external weeping, the seal-only specialist fix at £900-£1,400 is excellent value and should last 60k+ miles with revised seals. However, if the leak has caused coolant contamination or the engine has overheated, we recommend the full rebuilt route - contaminated oil galleries often cause turbo or bearing failure within 10k-15k miles of a partial repair.
A failed engine doesn't have to mean the end of your G Class. Whether you're dealing with an OM642 oil leak, an AMG turbo actuator failure, or a classic OM603 timing chain issue, EnginesMarket makes it simple to compare prices from trusted UK Mercedes Benz G Class specialists. Every rebuilt engine in our network includes upgraded components designed to address the original failure point, a minimum 12-month unlimited mileage warranty, and nationwide delivery with supply & fit options available.
Compare Mercedes Benz G Class Engine Replacement Prices Now →Disclaimer: All prices are indicative UK market ranges based on historical quote data and repair requests from our network of engine specialists. Dealer pricing is estimated based on published main dealer labour rates and genuine OEM parts pricing. Specialist pricing reflects actual quote data from EnginesMarket's UK network. Actual costs vary depending on damage severity, vehicle condition, variant, and workshop location within the UK. Use our free comparison tool to get tailored quotes for your specific Mercedes Benz G Class and engine code. Every engine supplied through EnginesMarket carries a minimum 12-month unlimited mileage warranty - always confirm exact terms with your chosen supplier.
Every engine type for your Mercedes Benz G Class is available through our UK network, with typical price ranges based on variant, engine code and budget.
All engine types include a minimum 12-month unlimited mileage warranty when sourced through EngineMarket. Prices are typical UK market ranges based on historical quote data from our network and depend on exact engine code, variant, mileage and supplier. Use our free comparison tool above - enter your registration to get tailored quotes for your specific Mercedes Benz G Class within hours.
Every displacement fitted to the Mercedes Benz G Class across all generations is listed below, with compatible engine codes, production years and common failure notes.
The 2.9-litre inline-six diesel arrived with the W463A generation G Class in 2019, replacing the long-serving OM642 V6. Codenamed OM656, this all-alloy unit introduced CAMTRONIC variable valve lift on the exhaust side and a two-stage turbocharger system producing exceptional 700Nm torque delivery from just 1,200rpm . Available initially as the G 400 d, the 2.9L later expanded to G 450 d variants, offering the most powerful diesel ever fitted to a G Class with 243kW output while maintaining refinement that eliminates traditional diesel clatter .
| Engine Code(s) | OM656 D29, OM656 |
| Compatible Models (UK) | G 400 d (2019-present), G 450 d |
| Production Years | 2024-present |
CAMTRONIC actuator seizure (A6560500001), coolant pump seal failure, AdBlue dosing module crystallisation on urban-driven vehicles
Mercedes Benz G Class Engines Fuel Type
The backbone of UK G Class sales since the W463 generation, diesel engines dominate replacement enquiries - particularly the OM642 V6 which powers approximately 70% of diesel models on British roads.
Not sure which fuel type your Mercedes Benz G Class has? Enter your registration number above to instantly identify your engine code, fuel system and compatible replacement options - all backed by a minimum 12-month unlimited mileage warranty from UK Mercedes Benz G Class specialists.
From the 1979 W460 military-spec original to the 2024 electrified W465 generation, this timeline covers every major engine fitted to the Mercedes-Benz G-Class - helping you identify your exact unit and compare rebuilt prices from UK specialists.
Not sure which year your Mercedes-Benz G-Class was built? Enter your registration number and we'll identify the exact engine, model year, and compatible replacement options instantly - all backed by a minimum 12-month warranty from UK Mercedes-Benz G-Class specialists.
FAQ
Question 1
A Mercedes G Class engine replacement typically costs between £4,500 and £15,000 depending on engine code, condition type, and whether fitting is included. OM642 diesels start around £4,800, while G63 AMG units range from £8,500 to £15,000.
Key points
Question 2
The OM642 is generally robust but has a known weak point - the oil cooler seals fail on ~80% of units after 60,000 miles, causing oil and coolant to mix. Address this preventatively and the engine easily exceeds 150,000 miles.
Key points
Question 3
The M157 (2012-2018) and M177 (2018-present) turbo actuators fail between 45,000-70,000 miles, causing limp mode and power loss. The M157 actuator (A1570940001) is the most frequent AMG G-Class failure driving replacement enquiries.
Key points
Question 4
No engine is fundamentally flawed, but high-mileage M157 (pre-2015) without documented turbo actuator replacement carries risk, and pre-2015 OM642 without oil cooler seal history needs immediate attention. Post-2018 OM656 diesel is the most reliable modern choice.
Key points
Question 5
A well-maintained G Class diesel engine regularly reaches 200,000-300,000 miles, with OM603/OM606 classics exceeding 300k. Petrol V8s typically last 150,000-200,000 miles before needing major work. The chassis itself can outlast multiple engines.
Key points
Question 6
Repair if the failure is isolated (e.g., oil cooler seals, turbo actuator, timing chain tensioner). Replace if there's bottom end damage, bore scoring, or multiple major failures. For G Classes worth £25,000+, a specialist rebuilt engine often makes more financial sense than chasing partial repairs.
Key points
Question 7
The OM656 3.0L straight-six diesel in the G400d returns approximately 11.9L/100km (24 mpg UK) in mixed driving - remarkably efficient for a 2.5-tonne brick-shaped SUV. The G63 AMG V8 averages just 13-14 mpg.
Key points
Question 8
Check your vehicle log book (V5C) for the engine number, which includes the engine code prefix (e.g., OM642, M176). Alternatively, enter your registration number in our tool above - we pull exact engine data from DVLA records instantly.
Key points
Question 9
We strongly advise against DIY fitting on a G Class. The complex 4MATIC system, gearbox alignment, and coding requirements demand specialist equipment and expertise. A poorly fitted engine can destroy the transfer case or cause electrical failures costing more than professional fitting.
Key points
Question 10
Every engine supplied through EngineMarket carries a minimum 12-month unlimited mileage warranty, with many specialists offering 24-month coverage on OM642 and AMG rebuilds. This includes parts and labour for any manufacturing defect or installation error.
Key points
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