BMW 8 Series M850i Engine ReplacementCompare Prices & Get Quotes
Get quotes today from trusted UK BMW 8 Series M850i engine specialists. Compare prices on reconditioned, rebuilt and used engines for your BMW M850i xDrive - with supply and fit options available nationwide.
Supply & Fit Available
12-Month Warranty
Nationwide Delivery
100+ Suppliers
From £6,000 to £10,000
Used from £3,500 · Reconditioned from £6,000 · Common codes: N63TU2, N63B44T3, S63TU
From £3,500
Tested, bare/short engine
From £6,000
Rod bearings addressed, tested
From quote
Upgraded bearings, full teardown, revised valvetrain
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3 Simple Steps3 Simple Stepsto Finding the Best BMW 8 Series M850i Replacement Engineto Finding the Best BMW 8 Series M850i Replacement Engine
Most replacements completed within 3-5 days.
Variant HistoryBMW 8 Series M850i - Engine History & Specs at a Glance
The BMW M850i xDrive launched in 2018 as the performance petrol flagship of the revived G15 8 Series range, sitting above the 840i and below the M8 Competition. Throughout its production life, the M850i has been powered exclusively by BMW's hot-vee N63/S63 V8 family, with power outputs ranging from 523hp to 530hp across its lifecycle.
Variant HistoryBMW 8 Series M850i - Engine History & Specs at a Glance
The BMW M850i xDrive launched in 2018 as the performance petrol flagship of the revived G15 8 Series range, sitting above the 840i and below the M8 Competition. Throughout its production life, the M850i has been powered exclusively by BMW's hot-vee N63/S63 V8 family, with power outputs ranging from 523hp to 530hp across its lifecycle.
BMW 8 Series M850i
Fuel TypePetrol
Engine Size Range4.4L V8 (single displacement across all years)
Power Output Range523-530hpEngine History Timeline
BMW 8 Series M850i xDrive launches with N63TU2 (4.4-litre twin-turbo V8 523hp)
Gran Coupe (G16) M850i xDrive introduced sharing the same N63TU2 engine
Engine calibration updates across all M850i variants
N63B44T3 designation appears in late production models
LCI facelift retains N63TU2/N63B44T3 architecture
Key Specs Snapshot
Fuel TypePetrolEngine Size Range4.4L V8 (single displacement across all years)Power Output Range523-530hpYears Produced2018-presentEvery BMW 8 Series M850i engine code ever fitted in the UK is covered below, with UK rebuilt pricing and known failure points.
BMW 8 Series M850i Engine Codes - Specifications & Replacement CostBMW 8 Series M850i Engine Codes - Specifications & Replacement Cost
4.4L Petrol V8 (2018-2024)
Power Output523hpYears Fitted2018-2024
Compatible Trim Levels
- M850i xDrive
- M850i xDrive Gran Coupe
- M850i xDrive Convertible
Find your exact engine code, specs and UK replacement cost guide.
Used
Tested, ready-to-fit engine
£3,500-£6,000
Reconditioned
Addressed known issues, tested
£6,000-£10,000
Rebuilt
Full teardown, upgraded internals
£8,000-£14,000
Common Failure
Hot-vee design leads to heat-related failures including valve stem seals, turbo coolant lines, and battery drain issues. Known as the "N63 nightmare" by specialists. Typically occurs from 60k-100k miles.
The BMW 8 Series M850i is powered exclusively by BMW's N63/S63 family of hot-vee twin-turbo V8s - an engine well-known in the specialist community for heat-related failures. Rebuilt BMW 8 Series M850i engines through EnginesMarket include upgraded components addressing the original failure points, plus a minimum 12-month unlimited-mileage warranty.
Why the BMW 8 Series M850i N63TU2 Wears Prematurely
Affected Vehicles
BMW 8 Series M850i (N63TU2/N63B44T3, 2018-present)
Typical Failure Mileage
60k-100k miles
Root Cause
The hot-vee architecture places turbos inside the V of the engine, generating significant heat that degrades valve stem seals over time. This leads to oil consumption, blue smoke on start-up, and eventual catalytic converter contamination if left unaddressed.
Why It Happens
The hot-vee architecture places turbos inside the V of the engine, generating significant heat that degrades valve stem seals over time. This leads to oil consumption, blue smoke on start-up, and eventual catalytic converter contamination if left unaddressed.
Dealer (parts + labour)
£3,000-£6,000
Specialist (parts + labour)
£2,000-£4,000
What it involves
Replacement of degraded seals without full engine removal (specialist jig required)
Suitability
Typically 40-60k miles of extended life on high-value M850i examples
1 - 2 daysDealer (parts + labour)
£14,000-£20,000+
Specialist (parts + labour)
£8,000-£14,000 (matches Section 4 N63TU2 rebuilt price)
What it involves
Complete rebuilt unit with upgraded valve seals, new turbo coolant lines, and 12-month warranty
Suitability
When labour to repair exceeds replacement cost, or engine has suffered additional damage
1 - 2 daysAll prices are indicative UK market ranges based on current UK specialist supplier data.| Repair Tier | Dealer (Parts + Labour) | Specialist (Parts + Labour) | What It Involves | Suitability | Estimated Time |
|---|---|---|---|---|---|
 Valve stem seal replacement Minor | £3,000-£6,000 | £2,000-£4,000 | Replacement of degraded seals without full engine removal (specialist jig required) | Typically 40-60k miles of extended life on high-value M850i examples | 1 - 2 days |
 Full Replacement - rebuilt engine Best Value | £14,000-£20,000+ | £8,000-£14,000 (matches Section 4 N63TU2 rebuilt price) | Complete rebuilt unit with upgraded valve seals, new turbo coolant lines, and 12-month warranty | When labour to repair exceeds replacement cost, or engine has suffered additional damage | 1 - 2 days |
Vehicle Value Check
Vehicle Value Check
A typical BMW 8 Series M850i from 2018-2021 sits in the £25,000-£45,000 range, dropping to £18,000-£30,000 for higher-mileage examples [THIRD-PARTY: AutoTrader UK market data 2025]. At these values, a full rebuilt engine replacement is almost always financially viable - the replacement cost represents 20-40% of vehicle value, well within the "safe" threshold.
Our Recommendation
Our Recommendation
If caught early (before full engine damage), the specialist valve stem seal replacement is the more cost-effective choice for the BMW 8 Series M850i. However, once contamination has affected the turbos or catalytic converters, a full rebuilt engine with upgraded components and warranty is the safer long-term decision for a car of this value.
Don't Let Engine Failure Write Off Your BMW 8 Series M850i
The BMW 8 Series M850i's N63 V8 is a powerful but complex engine. Specialist rebuilt units include upgraded components addressing the original failure points, with a minimum 12-month unlimited-mileage warranty. Compare prices from our UK-wide network - supply and fit available nationwide, often at significantly less than dealer replacement costs.
Compare rebuilt N63TU2 BMW 8 Series M850i engine prices
12-Month Minimum
UK Specialists Vetted
Best Price GuidanceImportant Information
Important Information
"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 BMW 8 Series M850i. Every engine supplied through EnginesMarket carries a minimum 12-month unlimited mileage warranty - always confirm exact terms with your chosen supplier."
BMW 8 Series M850i Engine ReplacementFrequently Asked Questions
Question 1How much does a BMW 8 Series M850i engine replacement cost in the UK-
A BMW 8 Series M850i engine replacement typically costs £6,000-£10,000 for a reconditioned unit (supply only), rising to £8,000-£14,000 for a fully rebuilt engine with warranty. Dealer replacement costs can reach £14,000-£20,000 plus labour.
- Used N63TU2 engines: £3,500-£6,000 (higher risk, lower warranty)
- Reconditioned N63TU2 engines: £6,000-£10,000 (tested, partial warranty)
- Rebuilt N63TU2 engines: £8,000-£14,000 (fully overhauled, 12-month warranty)
Question 2What are the signs of N63TU2 engine failure in an M850i-
Early warning signs of N63TU2 failure in the BMW 8 Series M850i include blue smoke on start-up (valve stem seals), cold-start rattle (timing chain tensioner), coolant loss (turbo coolant lines), and increased oil consumption.
- Blue smoke after idle: valve stem seals degrading
- Rattle on cold start: timing chain tensioner wear
- Coolant warning: check turbo coolant lines and fittings
Question 3Is it worth replacing the engine in a BMW 8 Series M850i-
Yes - with typical BMW 8 Series M850i values ranging from £25,000-£45,000 for 2018-2021 examples, a £6,000-£10,000 engine replacement represents just 20-40% of the car's value, making it financially viable.
- Vehicle value for M850i (2018-2021): £25,000-£45,000
- Replacement cost: 20-40% of vehicle value (safe threshold)
- Dealer replacement cost: often exceeds specialist pricing significantly
Question 4How long does a BMW 8 Series M850i engine replacement take-
A BMW 8 Series M850i engine replacement typically takes 12-16 hours of workshop labour for a specialist, with 16-22 hours at a main dealer due to hot-vee complexity.
- Specialist supply & fit: typically 3-5 working days
- Dealer replacement: often 5-7 working days
- Engine supply: nationwide delivery available, often next-day
Question 5What's the difference between M850i and M8 Competition engines-
The BMW 8 Series M850i uses the N63TU2/N63B44T3 4.4L V8 producing 523-530hp, while the BMW M8 Competition uses the S63TU high-output 4.4L V8 producing 625hp - the same displacement but significantly different power output and calibration.
- M850i N63TU2: 523hp, twin-turbo V8, GT-focused tuning
- M8 Competition S63TU: 625hp, higher boost, M-specific components
- Engine codes are different - do not interchange without expert compatibility checks
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