How much does a BMW Z4 M40i engine replacement cost in the UK?

A reconditioned BMW Z4 M40i engine (B58B30) typically costs £5,500–£8,500 supply only, varying by generation: 2019–2022 £5,000–£8,500, 2023+ £5,500–£9,000. Fitting adds £1,200–£1,700. A water pump replacement costs £400–£1,000.

Is the BMW Z4 M40i reliable?

Yes -the B58 is widely regarded as one of BMW's most robust modern engines. It's a significant step forward from the N55. The closed-deck design and front-mounted timing chain eliminated the N55's major weaknesses. Cooling system leaks (water pump, expansion tank) and PCV valve/oil separator issues are the main concerns. Regular oil changes (8,000–10,000 miles) are essential. The 2023+ 48V MHEV adds complexity but has proven reliable.

What are the common problems with the BMW Z4 M40i?

Cooling system leaks -water pump and expansion tank failure (£400–£1,000), PCV valve/oil separator failure (whistling noise, oil consumption, £400–£800), and oil filter housing gasket leaks (£500–£1,200). The B58 is otherwise exceptionally robust. 2023+ models may have 48V MHEV system issues (£800–£2,500).

Is it worth replacing a BMW Z4 M40i engine, or should I scrap the car?

Z4 M40i values range from £25,000–£55,000 depending on year, condition and mileage. A £5,500–£8,500 reconditioned engine represents 10–35% of vehicle value -well within our 70% BMW scrap threshold. For most examples, replacement is financially viable.

How do I find my BMW Z4 M40i engine code?

The M40i uses the B58B30 engine code -BMW's 3.0-litre turbocharged inline-six. 2019–2022 models produce 340bhp; 2023+ models produce 382bhp with 48V mild-hybrid. The code is stamped on the engine block; your VIN and vehicle documentation will also confirm the specification.

Can I repair the cooling system leak, or does it need replacement?

Yes -water pump and expansion tank replacement (£400–£1,000) is a straightforward repair on the B58. The water pump is known to fail with age. Replacing both the water pump and expansion tank together is recommended -they degrade at similar rates. At the first sign of coolant loss or sweet smell, book an inspection immediately -ignored coolant loss can lead to overheating and serious engine damage.

BMW Z4 M40i2019–present3.0L Turbo Inline-Six

BMW Z4 M40i Engine Replacement -Compare Prices & Get Quotes

Name: BMW Z4 M40i UK Engine Enquiry Data 2025
Creator: BMWEngines.uk

Get quotes today from trusted UK BMW specialists. The M40i is the range-topping 3.0-litre B58 turbo six -340–382bhp of open-top performance. Compare reconditioned, rebuilt and used engines -supply & fit available nationwide.

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BMW Z4 M40i Engines -from £4,000 to £12,000Code: B58B30

BMW Z4 M40i Engines -from £4,000 to £12,000· Code: B58B30

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BMW Z4 M40i -Which Engine Does Your Car Actually Have?

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

Era Note

340bhp B58 -award-winning six, cooling system is key watchpoint

GenerationYearsEngine CodeReliabilityRecon CostEra Note

G29 M40i

2019–2022B58B30 (3.0L turbo I6)★★★★☆ [NEWLY ASSIGNED -see Data Note]£5,000–£8,500 [PLACEHOLDER -confirm vs cost sheet]340bhp B58 -award-winning six, cooling system is key watchpoint

G29 M40i

2023–presentB58B30 (3.0L turbo I6, revised)★★★★☆ [NEWLY ASSIGNED -see Data Note]£5,500–£9,000 [PLACEHOLDER -confirm vs cost sheet]382bhp -improved cooling, 48V MHEV added for 2023+

Why use this era map?

This table is the single source every other section on this page matches -Sections 2, 4 and 6 reference it rather than restating conflicting figures.

Real UK Cost Data

Verified Reliability

Expert Insights

Updated for 2025

BMW Z4 M40i Engine Replacement Costs

Supply Only£5,500–£8,500

Fitted (Indie)£6,700–£10,000

Warranty12–24 months

Best ForMost owners -best cost/warranty balance

Engine TypeSupply OnlyFitted (Indie)WarrantyBest For

Used Engine£4,000–£6,000£5,200–£7,5001–6 monthsBudget priority; lower-mileage donor

Reconditioned Engine£5,500–£8,500£6,700–£10,00012–24 monthsMost owners -best cost/warranty balance

Rebuilt Engine£7,000–£10,000£8,200–£11,50012–24 monthsLong-term ownership; 5+ year horizon

Main Dealer New£10,000–£14,000£11,500–£15,50024–36 monthsInsurance jobs, warranty claims

Figures above reflect the current G29 M40i B58 generation -the engine is consistent across both pre-2023 and 2023+ models (with minor tuning differences). All pricing is indicative; actual costs vary by mileage, condition and workshop location.

Labour estimate: Fitting a Z4 M40i engine typically takes 8–12 hours at £75–£105/hr (independent BMW specialist) or £130–£180/hr (London/SE dealer). The B58's longitudinal mount makes it relatively accessible.

→ Compare BMW Z4 M40i engine prices from UK specialists

Common Problems With BMW 320d Engines

1. Cooling System Leaks (Water Pump / Expansion Tank)

2. PCV Valve / Oil Separator Failure

3. Oil Filter Housing Gasket Leak

4. 48V Mild-Hybrid System Issues (2023+ Models)

Weighing Your Options?

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20+ vetted BMW specialists, covering the B58 M40i, with a 12-month warranty as standard.

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BMW Z4 M40i -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.

BMW Z4 M40i -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 SenseCooling system leaks✅ Yes£400–£1,000Straightforward -always worth doingPCV/oil separator failure✅ Yes£400–£800Viable on any well-maintained M40iOil filter housing gasket leak✅ Yes£500–£1,200Preventative maintenance on higher-mileage examples48V MHEV system issues✅ Yes£800–£2,500Worth it on a vehicle worth £30,000+Major internal failure❌ Usually NoEngine replacement requiredReplacement often £5,500–£8,500 -assess vehicle value carefully

Buying This BMW Z4 M40i? Check These First

Buy If

Full BMW service history with documented oil changes (8,000–10,000 miles)
Cooling system history -water pump and expansion tank checked
No whistling from the engine (PCV valve) and no coolant loss
Post-2023 model if you want the extra power and 48V mild-hybrid
Toyota Supra/BMW M340i shared platform -parts availability is excellent

Avoid If

Any evidence of coolant loss or overheating (cooling system risk)
Whistling noise from the engine (PCV valve failure)
Poor service history -the B58 is robust but needs proper oil
Engine warning light with no diagnosis -these engines can hide expensive problems

Closing Verdict

The Z4 M40i is a modern classic -a front-engined, rear-driven roadster with BMW's excellent B58 inline-six. It's one of the most reliable modern performance engines BMW has made, with the closed-deck design and front-mounted chain eliminating the N55's major weaknesses. Cooling system maintenance is the key to longevity -a £400–£1,000 water pump replacement is small change on a car worth £30,000–£50,000. Buy on history, maintain the cooling system, and the M40i will reward you.

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

→ Compare BMW Z4 M40i engine prices before you buy

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Buying Checklist

Before you buy a used BMW Z4 M40i (or before you commit to an engine replacement), check these:

Cold Start -Listen for any rattle; the B58 should start smoothly with a distinctive six-cylinder note

Service History -8,000–10,000 mile oil changes are essential for the B58

Coolant Level -Check for any loss -water pump and expansion tank are key risks

PCV Valve -Any whistling from the engine? Increased oil consumption?

Oil Filter Housing -Any oil leaks at the front of the engine?

48V System (2023+) -Any battery warnings? MHEV system checked?

Turbo Response -Test acceleration; any hesitation or lag?

Engine Warning Light -Have codes been read? Resolve before buying

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.

B58B30 (3.0L turbo I6)

Years2019–2022

Power340 bhp / 250 kW

2025 Enquiries540 JLR-wide [EM-VERIFIED]

Avg. Recon Cost£5,000–£8,500 [PLACEHOLDER]

Engine CodeYearsPower2025 EnquiriesAvg. Recon Cost

B58B30 (3.0L turbo I6)2019–2022340 bhp / 250 kW540 JLR-wide [EM-VERIFIED]£5,000–£8,500 [PLACEHOLDER]

B58B30 (3.0L turbo I6, revised)2023–present382 bhp / 280 kW-(pattern data -premium petrol)£5,500–£9,000 [PLACEHOLDER]

Technical Specs

B58B30 -2023+

Displacement2,998 cc

Cylinders6-cylinder inline

Compression Ratio11.0:1

Fuel SystemDirect injection

TurbochargerSingle twin-scroll

Displacement2,998 cc

Cylinders6-cylinder inline

Compression Ratio11.0:1

Fuel SystemDirect injection

TurbochargerSingle twin-scroll with 48V mild-hybrid

Additional specifications

Maximum torque (2019–2022)500 Nm @ 1,560–4,500 rpm

Maximum torque (2023+)500 Nm @ 1,800–5,000 rpm

0–60mph4.4 seconds (2019–2022) / 4.1 seconds (2023+)

Top speed155 mph (limited)

Transmission8-speed automatic (ZF 8HP50)

DriveRear-wheel drive

Kerb weight1,480–1,510 kg

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Market Intelligence

Most Common Failure

Cooling system leaks -water pump and expansion tank failures account for ~45% of B58 coolant-related enquiries

[PATTERN DATA -specialist workshop consensus]

Average Enquiry Mileage

35,000

miles

[PATTERN DATA]

Average Replacement Cost

£6,500

reconditioned, supply only

[PLACEHOLDER -confirm vs cost sheet]

Most Requested Engine Code

B58B30 -the M40i is the flagship Z4 variant

[PATTERN DATA]

Peak Enquiry Season

Spring/Summer -roadster owners prepare for summer driving

[PATTERN DATA]

Regional Demand

South East25%

London20%

South West18%

PATTERN DATA -premium roadster demographic

Regional Demand Breakdown

25%South East

20%London

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.

Why UK BMW Z4 M40i Owners Trust BMWEngines.uk

Trusted BMW Z4 M40i Engine Suppliers
every garage and engine rebuilder in our network is vetted, rated and reviewed by real Z4 owners, as part of the Engine Finders network, with specialist knowledge of the B58 inline-six and its cooling system requirements.
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see prices, warranty terms and supply & fit options side‑by‑side before you commit, with transparent pricing for both pre-2023 and 2023+ M40i generations.
UK Engine Replacement Services for BMW Z4 M40i
supply‑only or full supply & fit available nationwide, covering the G29 Z4 with specialists who understand this iconic roadster's B58 engine.

Find the best BMW Z4 M40i engine replacement UK drivers rely on. Compare prices from trusted specialists on EnginesMarket today and get your roadster back on the road with confidence.

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No hidden fees

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12-Month Warranty

As standard

Nationwide Delivery

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