BMW Z1 25i Engine ReplacementCompare Prices & Get Quotes
Get quotes today from trusted UK BMW Z1 25i engine specialists. Compare prices on reconditioned, rebuilt and used M20B25 engines for your iconic Z1 roadster - supply & fit available nationwide.
Supply & Fit Available
12-Month Warranty
Nationwide Delivery
100+ Suppliers
From £2,500 to £6,000
Used from £1,200 · Reconditioned from £2,200 · Common codes: M20B25, M20B25 (256K1)
From £1,200
Tested, bare/short engine
From £2,200
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 Z1 25i Replacement Engineto Finding the Best BMW Z1 25i Replacement Engine
Most replacements completed within 3-5 days.
Variant HistoryBMW Z1 25i - Engine History & Specs at a Glance
The BMW Z1 25i arrived in 1989 as BMW's first dedicated roadster since the 507, powered exclusively by the M20B25 2.5-litre straight-six from the E30 325i. With just 8,000 units produced between 1989 and 1991, the Z1 is one of the rarest BMW models ever built - and the sole drivetrain specification remained unchanged throughout its brief production run.
Variant HistoryBMW Z1 25i - Engine History & Specs at a Glance
The BMW Z1 25i arrived in 1989 as BMW's first dedicated roadster since the 507, powered exclusively by the M20B25 2.5-litre straight-six from the E30 325i. With just 8,000 units produced between 1989 and 1991, the Z1 is one of the rarest BMW models ever built - and the sole drivetrain specification remained unchanged throughout its brief production run.
BMW Z1 25i
Fuel TypePetrol
Engine Size2.5L (2,494cc)
Power Output170hp (125kW) at 5,800rpmEngine History Timeline
March 1989 - BMW Z1 25i production begins with the M20B25 2.5-litre straight-six petrol engine producing 170hp and 222Nm of torque
1991 - Z1 production continues with the M20B25 engine unchanged; all UK-market cars are left-hand drive
June 1991 - Z1 production ends after 8,000 units; no engine changes were made during the production run
Key Specs Snapshot
Fuel TypePetrolEngine Size2.5L (2,494cc)Power Output170hp (125kW) at 5,800rpmTorque222Nm (164lb-ft) at 4,300rpmEngine ManagementBosch Motronic 1.3TransmissionGetrag 260/5 5-speed manualYears Produced1989-1991Every engine fitted to the BMW Z1 25i is covered below, with UK rebuilt pricing and known failure points.
BMW Z1 25i Engine Codes - Specifications & Replacement CostBMW Z1 25i Engine Codes - Specifications & Replacement Cost
2.5L Petrol (1989-1991)
Power Output170hp (125kW) at 5,800rpmTorque222Nm (164lb-ft) at 4,300rpmDisplacement2,494ccEngine ManagementBosch Motronic 1.3ValvetrainSOHC, 2 valves per cylinder, belt-driven camshaftYears Fitted1989-1991 (all Z1 production)
Compatible Trim Levels
- Z1 2.5i
- Z1 25i
Find your exact engine code, specs and UK replacement cost guide.
Used
Tested, ready-to-fit engine
£1,200-£2,500
Reconditioned
Addressed known issues, tested
£2,200-£4,000
Rebuilt
Full teardown, upgraded internals
£2,500-£6,000
Common Failure
The M20B25 is generally robust but suffers from several age-related issues. Head gasket failure is common, leading to coolant leaks and overheating. Oil leaks develop around the valve cover and oil pan. The timing belt requires strict 60,000-mile replacement intervals - failure is catastrophic. The Z1's unique low ride height (40mm lower than E30) causes oil pump sump angle issues, leading to oil starvation and camshaft wear. The under-body exhaust heat shield can fail, cooking the starter motor. Cooling system components (water pump, thermostat) degrade with age.
The BMW Z1 25i is powered exclusively by the M20B25 2.5-litre straight-six - a robust and characterful engine shared with the E30 325i. However, with Z1 production ending in 1991, all examples are now 30+ years old, and age-related failures are common. Every rebuilt M20B25 engine supplied through EnginesMarket includes upgraded components addressing the original failure points - plus a minimum 12-month unlimited mileage warranty.
Why the BMW Z1 25i M20B25 Requires Strict Maintenance
Affected Vehicles
BMW Z1 25i (M20B25, 1989-1991)
Typical Failure Mileage
60,000 miles (belt interval) / immediate if neglected
Root Cause
The M20B25 uses a rubber timing belt rather than a chain. If the belt breaks, pistons strike valves - catastrophic engine failure requiring full replacement. The belt should be replaced every 60,000 miles or 5 years, whichever comes first.
Why It Happens
The M20B25 uses a rubber timing belt rather than a chain. If the belt breaks, pistons strike valves - catastrophic engine failure requiring full replacement. The belt should be replaced every 60,000 miles or 5 years, whichever comes first.
Dealer (parts + labour)
£500-£800
Specialist (parts + labour)
£350-£600
What it involves
Replace timing belt, tensioner, water pump, thermostat
Suitability
60,000 miles / 5 years. Essential preventative maintenance
1 - 2 daysDealer (parts + labour)
£4,000-£6,500
Specialist (parts + labour)
£2,500-£5,000
What it involves
Supply & fit rebuilt M20B25 with new timing components, 12-month warranty
Suitability
Required if belt snapped causing valve/piston 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 |
|---|---|---|---|---|---|
 Preventative - timing belt & water pump replacement Minor | £500-£800 | £350-£600 | Replace timing belt, tensioner, water pump, thermostat | 60,000 miles / 5 years. Essential preventative maintenance | 1 - 2 days |
 Full Replacement - rebuilt/reconditioned engine (catastrophic failure) Best Value | £4,000-£6,500 | £2,500-£5,000 | Supply & fit rebuilt M20B25 with new timing components, 12-month warranty | Required if belt snapped causing valve/piston damage | 1 - 2 days |
Vehicle Value Check
Vehicle Value Check
A typical BMW Z1 25i in the UK is worth between £20,000 and £50,000 depending on condition and mileage, with low-mileage examples commanding significantly higher prices. With a full rebuilt engine costing £2,500-£5,000 fitted, replacement cost is typically small relative to vehicle value - making engine replacement a financially viable option for most Z1 owners. However, given the Z1's collector-car status, using a specialist with M20B25 experience is essential to protect your investment.
Our Recommendation
Our Recommendation
If you own a Z1 25i and do not have documented evidence of a recent timing belt change, replace it immediately - the belt is the single most critical maintenance item on the M20B25. A £350-£600 specialist job is far cheaper than a £2,500-£5,000 engine replacement. If the belt has already snapped, a rebuilt M20B25 with upgraded components is the only reliable solution.
Don't Let Engine Failure Write Off Your BMW Z1 25i
A failed M20B25 engine doesn't have to mean the end of the road for your Z1 25i. Whether you're facing timing belt failure, Z1-specific oil starvation, head gasket issues, or heat shield problems, EnginesMarket connects you with trusted UK BMW specialists who supply rebuilt M20B25 engines with upgraded components specifically designed to address these original failure points. Every engine comes with a minimum 12-month unlimited mileage warranty, nationwide delivery, and supply & fit options across the UK. Compare prices today - and keep your iconic Z1 on the road without paying the main dealer premium.
Compare rebuilt M20B25 BMW Z1 25i 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 Z1 25i. Every engine supplied through EnginesMarket carries a minimum 12-month unlimited mileage warranty - always confirm exact terms with your chosen supplier."
BMW Z1 25i Engine ReplacementFrequently Asked Questions
Question 1How much does a BMW Z1 25i engine replacement cost in the UK-
A full BMW Z1 25i engine replacement typically costs £2,500-£6,000 supply-only for a rebuilt M20B25 unit, or £4,000-£6,500 fitted by a specialist.
- Used M20B25 engines: £1,200-£2,500 depending on mileage and condition
- Reconditioned units: £2,200-£4,000
- Professional fitting adds £1,000-£2,000 to the engine cost
Question 2Is the BMW Z1 25i M20B25 engine reliable-
The M20B25 is one of BMW's most robust and characterful straight-six engines, shared with the E30 325i. However, Z1-specific issues exist: the unique cylinder-head oil-feed restriction starves the valvetrain on 1989-1991 models, and the under-body exhaust heat-shield failure cooks starter motors. The Z1 sits 40mm lower than the E30, flattening the sump angle and causing oil starvation at low RPM - a fault never seen in the E30. Regular maintenance, particularly timing belt replacement every 60,000 miles, is essential.
-> Get quotes for BMW Z1 25i M20B25 engine repairs and replacementQuestion 3What are the signs of timing belt failure in a BMW Z1 25i M20B25-
The M20B25 uses a rubber timing belt that must be replaced every 60,000 miles or 5 years. Warning signs include:
- No warning - the belt typically snaps without prior symptoms
- Rattling or squealing noise from the front of the engine
- Engine misfire or loss of power if belt has jumped a tooth
- Complete engine seizure - if the belt snaps, pistons strike valves
Question 4Is it worth replacing the engine on a BMW Z1 25i-
For a Z1 25i worth £20,000-£50,000, a £2,500-£5,000 rebuilt engine is typically good value - replacement cost is small relative to vehicle value.
- Compare replacement cost against vehicle value - replacement is viable up to approximately 70% of the car's value
- Given the vehicle's collector-car status, specialist rebuild with warranty is the safest option
- Always factor the 12-month warranty into your replacement decision
Question 5What causes the BMW Z1 25i M20B25 oil starvation problem-
The Z1 sits 40mm lower than the E30 325i, which flattens the sump angle and alters oil pickup geometry. This causes oil starvation at low RPM, leading to camshaft lobe pitting and wear - a fault never seen in the E30.
- Symptoms include ticking or tapping from the top end
- Camshaft pitting is visible on inspection
- The fix is an up-rated oil pump (OEM 11 41 1 730 302) and hardened 731 camshaft
Question 6Can I replace my BMW Z1 25i engine with a different engine-
Engine swaps to a different size or type are technically complex and rarely cost-effective for the Z1 25i:
- The M20B25 is the only engine fitted to the Z1 from the factory - stick to like-for-like replacement
- Swapping to an M50 or S50 requires different ECU, wiring, engine mounts, and transmission
- The Z1's unique chassis and low ride height make non-standard swaps extremely difficult
- Insurance must be notified of any non-standard engine swap
- Our marketplace only recommends like-for-like code-matching for warranty coverage
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