BMW Z4 M40i2019–present3.0L Turbo Inline-Six
BMW Z4 M40i Engine Replacement -Compare Prices & Get Quotes
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
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BMW Z4 M40i -Which Engine Does Your Car Actually Have?
Two generations. Two eras. One guide to reliability, costs and what really matters.
Era Note
340bhp B58 -award-winning six, cooling system is key watchpoint
Era Note
382bhp -improved cooling, 48V MHEV added for 2023+
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 UKCost Data
- VerifiedReliability
- ExpertInsights
- Updated for2025
BMW Z4 M40i Engine Replacement Costs
- Supply Only£4,000 – £6,000
- Fitted (Indie)£5,200 – £7,500
- Warranty1–6 months
- Best ForBudget priority; lower-mileage donor
- Supply Only£5,500 – £8,500
- Fitted (Indie)£6,700 – £10,000
- Warranty12–24 months
- Best ForMost owners -best cost/warranty balance
- Supply Only£7,000 – £10,000
- Fitted (Indie)£8,200 – £11,500
- Warranty12–24 months
- Best ForLong-term ownership; 5+ year horizon
- Supply Only£10,000 – £14,000
- Fitted (Indie)£11,500 – £15,500
- Warranty24–36 months
- Best ForInsurance 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.
Common Problems With BMW Z4 M40i Engines
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.
Z4 M40i -Repair, Buy, or Replace?
Not every issue means a new engine.Here’s what can be repaired, when it makes sense, and what to check before you buy.
Can It Be Repaired?
| Problem | Repairable? | Typical Cost | When It Makes Sense |
|---|---|---|---|
| Cooling system leaks | Yes | £400 – £1,000 | Straightforward -always worth doing |
| PCV/oil separator failure | Yes | £400 – £800 | Viable on any well-maintained M40i |
| Oil filter housing gasket leak | Yes | £500 – £1,200 | Preventative maintenance on higher-mileage examples |
| 48V MHEV system issues | Yes | £800 – £2,500 | Worth it on a vehicle worth £30,000+ |
| Major internal failure | Usually No | Engine replacement required | Replacement often £5,500–£8,500 -assess vehicle value carefully |
ProblemRepairable? · Typical Cost
Cooling system leaks
Yes£400 – £1,000
Straightforward -always worth doing
PCV/oil separator failure
Yes£400 – £800
Viable on any well-maintained M40i
Oil filter housing gasket leak
Yes£500 – £1,200
Preventative maintenance on higher-mileage examples
48V MHEV system issues
Yes£800 – £2,500
Worth it on a vehicle worth £30,000+
Major internal failure
Usually NoEngine replacement required
Replacement 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.
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Buying Checklist
Before you buy a used BMW Z4 M40i (or before you commit to an engine replacement), check these:
1. Cold Start -Listen for any rattle; the B58 should start smoothly with a distinctive six-cylinder note
2. Service History -8,000–10,000 mile oil changes are essential for the B58
3. Coolant Level -Check for any loss -water pump and expansion tank are key risks
4. PCV Valve -Any whistling from the engine? Increased oil consumption?
5. Oil Filter Housing -Any oil leaks at the front of the engine?
6. 48V System (2023+) -Any battery warnings? MHEV system checked?
7. Turbo Response -Test acceleration; any hesitation or lag?
8. Engine Warning Light -Have codes been read? Resolve before buying
Buying Checklist
Before you buy a used BMW Z4 M40i (or before you commit to an engine replacement), check these:
- 1
Cold Start -Listen for any rattle; the B58 should start smoothly with a distinctive six-cylinder note
- 2
Service History -8,000–10,000 mile oil changes are essential for the B58
- 3
Coolant Level -Check for any loss -water pump and expansion tank are key risks
- 4
PCV Valve -Any whistling from the engine? Increased oil consumption?
- 5
Oil Filter Housing -Any oil leaks at the front of the engine?
- 6
48V System (2023+) -Any battery warnings? MHEV system checked?
- 7
Turbo Response -Test acceleration; any hesitation or lag?
- 8
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 Z4 M40i pitfalls.
Engine Codes
This table's rows match Section 1B's Era Map exactly.
B58B30 (3.0L turbo I6)
- Years
- 2019–2022
- Power
- 340 bhp / 250 kW
- 2025 Enquiries
- 540 JLR-wide[EM-VERIFIED]
- Avg. Recon Cost
- £5,000–£8,500[PLACEHOLDER]
B58B30 (3.0L turbo I6, revised)
- Years
- 2023–present
- Power
- 382 bhp / 280 kW
- 2025 Enquiries
- —(pattern data -premium petrol)
- Avg. Recon Cost
- £5,500–£9,000[PLACEHOLDER]
Technical SpecsB58B30 -2023+
- Displacement
- 2,998 cc
- Cylinders
- 6-cylinder inline
- Compression Ratio
- 11.0:1
- Fuel System
- Direct injection
- Turbocharger
- Single twin-scroll
- Displacement
- 2,998 cc
- Cylinders
- 6-cylinder inline
- Compression Ratio
- 11.0:1
- Fuel System
- Direct injection
- Turbocharger
- Single 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
- 0–60mph
- 4.4 seconds (2019–2022) / 4.1 seconds (2023+)
- Top speed
- 155 mph (limited)
- Transmission
- 8-speed automatic (ZF 8HP50)
- Drive
- Rear-wheel drive
- Kerb weight
- 1,480–1,510 kg
Market Intelligence
Real data from thousands of Z4 M40i enquiries in 2025.
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 East
- 25%
- London
- 20%
- South West
- 18%
- Other Regions
- 37%
Regional Demand Breakdown
20%London25%South East18%South West37%Other Regions
Frequently Asked Questions
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.
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.
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).
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.
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.
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.
Disclaimer: 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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UK Engine Replacement Services for BMW Z4 M40i
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