BMW X4 M40i Engine Replacement Compare Prices & Get Quotes

A rebuilt B58 engine for the BMW X4 M40i typically costs £4,500-£8,500 supply-only, depending on the exact B58 variant and specification. Specialist fitting adds £650-£910 (10-14 hours labour at independent rates). Main dealer replacement can be significantly higher - often £9,000+ for a new engine.

• Rebuilt B58 supply-only: £4,500-£8,500
• Used B58: £2,000-£3,800
• Specialist fitting: £650-£910

The B58 is widely considered BMW's most reliable modern six-cylinder petrol engine. With proper maintenance, it routinely exceeds 150,000-200,000 miles without major failures .

• Closed-deck block design provides exceptional strength
• Common minor issues: oil filter housing leaks, coolant cap failure, PCV valve
• Well-maintained B58 engines last 300,000+ km before major work is needed

The plastic oil filter housing in the B58 can become brittle and develop cracks, leading to oil or coolant leaks. Look for oil spots under the car, low oil levels between services, or coolant loss without visible external leaks .

• Average lifespan of the plastic housing: approximately 8 years
• Housing replacement at a specialist: £900-£1,500
• Ignoring the leak can lead to oil starvation and engine damage

Yes, if the body and transmission are sound. A £4,500-£8,500 rebuilt B58 engine can add 100,000+ miles to a well-maintained X4 M40i - far cheaper than replacing the whole vehicle, which typically retains strong value at £18,000+.

• A 2018 X4 M40i with 100k miles is worth £15,000-£22,000 - replacement makes financial sense
• Rebuilt B58 includes upgraded components addressing original failure points
• Compare to buying another used M40i with unknown engine history
• Typical rebuilt B58 lifespan: 100,000+ miles with proper maintenance

Professional replacement includes ISN (Individual Serial Number) coding to match the replacement engine to your X4 M40i's immobiliser and ECU. Never skip this step.

• ISN coding ensures the engine starts and runs with your car's security system
• Without correct coding, the immobiliser will prevent engine operation
• All EnginesMarket specialists include ISN matching and DDE calibration
• The 48V MHT system (2021+) also requires hybrid system recalibration

The X4 M40i MHT (2021-2024) adds a 48V mild hybrid system with an 11hp electric boost and coasting functionality. The base B58 engine remains fundamentally the same, but the MHT system adds complexity.

• MHT adds 11hp electric assistance under acceleration
• MHT enables engine-off coasting for improved fuel economy
• MHT components (starter-generator, 48V battery) are BMW-specific
• MHT engine replacement requires professional 48V system isolation