How much does a BMW M850i engine replacement cost in the UK?

A reconditioned N63 engine typically costs £9,000–£17,000 supply only, with used units available from £3,000–£6,500. Fitting adds £2,000–£3,000. Use our calculator for a figure specific to your car.

Is the BMW M850i engine reliable?

The N63 has a notorious reputation. Early versions (2008–2013) were genuinely unreliable - timing chain failures, excessive oil consumption, and turbocharger issues were common. The M850i's N63TU3 is the most refined iteration, with many issues addressed. However, diligent maintenance - especially frequent oil changes (3,500–5,000 miles) - is absolutely essential.

What are the common problems with the BMW M850i?

Timing chain stretch and guide failure (the most severe issue), excessive oil consumption and valve stem seal leaks, turbocharger failure, and cooling system problems. The 2019 model also had a high-pressure fuel pump recall.

Is it worth replacing a BMW M850i engine, or should I scrap the car?

M850i values remain strong - a well-kept example is often worth £30,000–£60,000+. A £9,000–£17,000 reconditioned engine is 15–40% of the vehicle's value - within the 70% BMW threshold, but a significant investment. Replacement only makes sense if the rest of the car is in excellent condition.

How do I find my BMW M850i engine code?

The engine code is N63B44T3 or N63B44D - it's the only engine used in the G14/G15/G16 M850i. You can find it on the VIN plate, in the vehicle documentation, or on a label on the engine itself.

Can I repair the N63 timing chain, or does it need replacement?

It needs replacement - the chain guides break and the tensioner wears. A full timing chain, tensioner, guide and VANOS sprocket replacement costs £3,000–£6,000. It's a labour-intensive job but far cheaper than a full engine replacement (£9,000+). At the first sign of rattling from the front of the engine, book an inspection immediately.

BMW 8 Series M850i2018–present4.4-litre Twin-Turbo V8

BMW M850i Engine Replacement — Compare Prices & Get Quotes

The M850i is powered by BMW's N63 4.4-litre twin-turbo V8 - 530 hp and 750 Nm of torque in its latest, most refined form. It's a masterpiece of engineering, but one with a notorious reputation. Get quotes from UK specialists for reconditioned, rebuilt and used units today.

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BMW M850i Engines - from £3,000 to £17,000Code: N63B44T3 / N63B44D

BMW M850i Engines - from £3,000 to £17,000· Code: N63B44T3 / N63B44D

Instant QuotesNo Obligation100% FreeReconditionedRebuiltUsedSupply & Fit AvailableUK-Wide Network

The M850i THROUGH TIME - Era Map

Four generations. Four eras. One guide to reliability, costs and what really matters.

GenerationYearsEngine CodeReliabilityRecon CostEra Note

Why use this era map?

Every cost guide, reliability rating and engine code on this page is aligned to the data above. This keeps everything consistent and trustworthy.

Real UK Cost Data

Verified Reliability

Expert Insights

Updated for 2025

BMW M850i Engine Replacement Costs

Supply Only£9,000–£13,000

Fitted (Indie)£11,000–£15,000

Warranty12–24 months

Best ForMost owners - best cost/warranty balance

Engine TypeSupply OnlyFitted (Indie)WarrantyBest For

Used Engine£3,000–£6,500£5,000–£8,5001–6 monthsBudget priority; lower‑mileage examples

Reconditioned Engine£9,000–£13,000£11,000–£15,00012–24 monthsMost owners - best cost/warranty balance

Rebuilt Engine£12,000–£17,000£14,000–£19,00012–24 monthsLong-term ownership; 3+ year horizon

Main Dealer New£15,000–£20,000+£17,000–£23,000+24–36 monthsInsurance jobs, warranty claims

Figures above reflect the current M850i market. A replacement N63B44D motor costs approximately £12,525 on average, with new or reconditioned units reaching up to £16,819. Fitting adds £2,000–£3,000. See the Era Map above for generation-specific context.

Labour estimate: Fitting an M850i V8 engine typically takes 16–22 hours at £65–£95/hr (independent) or £110–£160/hr (London/SE dealer). The N63's "hot-vee" design makes some repairs exceptionally labour-intensive.

→ Compare M850i engine prices from UK specialists

Common Problems With BMW 320d Engines

1. Timing Chain Stretch and Guide Failure

Symptoms: Rattling noise on cold start, metallic ticking from the front of the engine, engine warning light, cam timing errors, eventual chain slip

Typical mileage: 60,000–100,000 miles

Repair cost: £3,000–£6,000 (timing chain, tensioner, guides and VANOS sprocket replacement)

Replacement cost: £9,000–£13,000 (if chain jumps and causes valve interference)

🔴 Immediate - any rattling from the front of the engine on an N63 requires immediate investigation

Our recommendation:

The N63's timing chain guides are made of brittle plastic that can break apart, sending metal fragments through the engine. The "hot-vee" design generates extreme heat loads that accelerate component wear. This is one of the most severe and common problems on the N63. BMW faced class action lawsuits over N63 timing chain and oil consumption issues. If you hear any rattling from the front of the engine, book an inspection immediately. A preventative chain replacement is far cheaper than a full engine replacement.

Read the full timing chain failure guide

1. Timing Chain Stretch and Guide Failure

Symptoms: Rattling noise on cold start, metallic ticking from the front of the engine, engine warning light, cam timing errors, eventual chain slip

Typical mileage: 60,000–100,000 miles

Repair cost: £3,000–£6,000 (timing chain, tensioner, guides and VANOS sprocket replacement)

Replacement cost: £9,000–£13,000 (if chain jumps and causes valve interference)

🔴 Immediate - any rattling from the front of the engine on an N63 requires immediate investigation

Our recommendation:

Read the full timing chain failure guide

2. Excessive Oil Consumption and Valve Stem Seal Leaks

Symptoms: Oil level dropping between services, blue smoke on cold start or after idling, low oil pressure warning, puff of smoke when accelerating

Typical mileage: 50,000–100,000 miles

Repair cost: £2,500–£5,000 (valve stem seal replacement)

Replacement cost: £9,000–£13,000 (if oil starvation causes bottom-end damage)

🔴 Immediate - the N63 can burn up to a quart of oil in 1,000 miles

Our recommendation:

The N63 is notorious for excessive oil consumption. This is caused by valve stem seal leaks, turbocharger oil seal failure, and PCV system issues. BMW even launched a Customer Care Package program to address widespread issues. Check oil levels regularly - if you're topping up more than 1L between services, have the valve stem seals and turbochargers inspected. Ignoring oil consumption can lead to catastrophic engine failure.

Read the full valve stem seal failure guide

3. Turbocharger Failure and Cooling System Issues

Symptoms: Loss of power, whistling or grinding noise from the engine bay, blue or black smoke, engine warning light, overheating

Typical mileage: 60,000–120,000 miles

Repair cost: £2,000–£5,000 (turbocharger replacement and cooling system service)

Replacement cost: £9,000–£13,000 (if turbo failure causes engine damage)

🟠 Check - book inspection urgently

Our recommendation:

The N63's twin turbochargers are crammed into a tight engine bay, generating extreme heat loads that overwhelm cooling systems and accelerate component wear. The 2019 M850i also had a recall for high-pressure fuel pump flanges that could crack, causing fuel leaks. Extended oil change intervals (recommended by BMW) cause coking issues in the hot-vee engine. Many specialists recommend oil changes every 3,500–5,000 miles instead. If you notice any whistling, loss of power, or overheating, have the turbochargers and cooling system inspected immediately.

Read the full turbocharger failure guide

Weighing Your Options?

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M850i - Repair, Buy, or Replace?

Every 320d has a story. Make the right call with clear data, real-world costs, and honest guidance from UK specialists.

M850i - Repair, Buy, or Replace?

Every 320d has a story. Make the right call with clear data, real-world costs, and honest guidance from UK specialists.

Can It Be Repaired?

ProblemRepairable?Typical CostWhen It Makes SenseTiming chain (preventative)✅ Yes£3,000–£6,000Labour-intensive but far cheaper than a full engine replacementTiming chain failure (engine damage)❌ Usually NoEngine replacementIf chain jumps and valves hit pistons, replacement is the only optionValve stem seals✅ Yes£2,500–£5,000Specialist job - far cheaper than a new engineTurbocharger failure✅ Yes£2,000–£5,000Turbo replacement - catch before debris damages the engineHigh-pressure fuel pump (recall)✅ YesFree (under recall)BMW recall covered 2019 M850i models

Buying This M850i? Check These First

Buy If

Full service history with frequent oil changes (3,500–5,000 mile intervals - not BMW's extended schedule)
Evidence of timing chain inspection or replacement
No blue smoke on cold start - valve stem seals should be healthy
A well-maintained example where the previous owner understood the N63's needs

Avoid If

Any rattling from the front of the engine - timing chain issues are likely
Blue smoke on cold start - valve stem seals are failing
Poor service history - the N63 is unforgiving of neglect
Evidence of oil consumption without a diagnosed fix
Any engine warning light without a clear diagnosis

Closing Verdict

The M850i is a genuine grand tourer - 530 hp, 750 Nm, 0–62 mph in 3.9 seconds. The N63 V8 that powers it is a masterpiece of engineering, but one with a notorious reputation. Early N63s (2008–2013) were genuinely unreliable. The M850i's N63TU3 is the most refined iteration, but it still carries the hot-vee V8's legacy. Buy on history, maintain religiously (oil changes every 3,500–5,000 miles), and the M850i will reward you with one of BMW's finest driving experiences. Skip the history and it will punish you.

Don't guess.Get the right engine at the right price.

→ Compare M850i engine prices before you buy

Don't Guess. Compare.

Get real quotes from vetted UK specialists and make the right call for your 320d.

→ Compare M850i engine prices before you buy

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Buying Checklist

Before you buy a used BMW M850i (or before you commit to an engine replacement), check these:

1. Cold Start

Any blue smoke? (valve stem seal warning - a critical check on the N63)

2. Rattling

Any rattling from the front of the engine? (timing chain warning)

3. Oil Consumption

How much oil does it use between services? (N63s are known for oil thirst)

4. Service History

including evidence of frequent oil changes (3,500–5,000 mile intervals recommended)

5. Coolant Level

Any unexplained loss? (cooling system warning)

6. Turbo Performance

Test acceleration; any whistling, hesitation, or loss of power?

7. Recall Check

Has the high-pressure fuel pump recall been completed? (2019 models)

8. MOT History

Check for emissions-related failures (catalyst, O2 sensors)

Buy smart. Drive with confidence.

A few checks today can save thousands tomorrow. Use this checklist to avoid the most common 320d pitfalls.

Buy smart. Drive with confidence.

A few checks today can save thousands tomorrow. Use this checklist to avoid the most common 320d pitfalls.

BMW 320d Engine Codes

This table's rows match Section 1B's Era Map exactly - one engine across all three M850i body styles.

N63B44T3 / N63B44D

Years2018–present

Power530 hp

2025 Enquiries[PATTERN DATA]

Avg. Recon Cost£9,000–£17,000 [BMW-QUOTE]

Engine CodeYearsPower2025 EnquiriesAvg. Recon Cost

N63B44T3 / N63B44D2018–present530 hp[PATTERN DATA]£9,000–£17,000 [BMW-QUOTE]

Technical Specs

N63B44T3 / N63B44D

Displacement4,395 cc (4.4-litre)

CylindersV8

Compression Ratio10.0:1

Fuel SystemDirect injection

TurbochargerTwin-turbo (hot-vee design)

ValvetrainDOHC, 4 valves per cylinder, Double-VANOS, Valvetronic

TransmissionZF 8HP76 8-speed automatic

→ Compare M850i engine prices for your BMW

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Market Intelligence

Most Common Failure

Timing chain stretch and guide failure

the defining risk of the N63 V8

Average Enquiry Mileage

40,000

–80,000 miles【PATTERN DATA】

Average Replacement Cost

£9,000

–£17,000 reconditioned, supply only【BMW-QUOTE】

Most Requested Engine Code

N63B44T3

the M850i's twin-turbo V8【PATTERN DATA】

Peak Enquiry Season

Spring

performance car season【PATTERN DATA】

Regional Demand

London22%

South East18%

South West (14%)【PATTERN DATA】

Regional Demand Breakdown

22%London

18%South East

BMW 320d - Frequently Asked Questions

All prices are indicative UK market ranges based on historical quote data from our network of engine specialists. Actual costs vary by variant, engine code, damage severity and workshop location. Use our free comparison tool to get tailored quotes. Every engine supplied through EnginesMarket carries a minimum 12-month unlimited-mileage warranty - always confirm terms with your chosen supplier.

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Compare M850i Engine Replacement Companies
see prices, warranty terms and supply & fit options side‑by‑side before you commit, with specialists who genuinely understand the N63's timing chain, oil consumption and cooling system nuances.
UK Engine Replacement Services for M850i
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12-Month Warranty

As standard

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