BMW Z4 sDrive18i / sDrive20i2009–present2 Engine Generations
BMW Z4 sDrive18i / sDrive20i Engine Replacement —Compare Prices &
Get Quotes
Get quotes today from trusted UK BMW Z4 specialists. Compare reconditioned, rebuilt and used 2.0-litre turbocharged petrol engines — N20 and B48 variants across the E89 and G29 generations — supply & fit available nationwide.
- Supply &Fit Available
- 12-MonthWarranty
- NationwideDelivery
- 20+Specialists
BMW Z4 sDrive18i / sDrive20i Engines — from £800 to £6,500Common codes: N20B20A, B48B20A
- Instant Quotes
- No Obligation
- 100% Free
- Reconditioned
- Rebuilt
- Used
- Supply & Fit Available
- UK-Wide Network
- Instant Quotes
- No Obligation
- 100% Free
- Reconditioned
- Rebuilt
- Used
- Supply & Fit Available
- UK-Wide Network
The Z4 sDrive18i / sDrive20i Through Time — Era Map
Two generations. Two eras. One guide to reliability, costs and what really matters.
Era Note
2.0L turbo four — 156–184 bhp; timing chain guide failure is the critical weakness; pre-2015 units most at risk
Era Note
2.0L turbo four — 184–197 bhp; improved B48 design; oil filter housing leaks and coolant system are primary concerns
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 sDrive18i / sDrive20i Engine Replacement Costs
- Supply Only£800 – £2,000
- Fitted (Indie)£1,400 – £3,200
- Warranty1–6 months
- Best ForBudget priority; vehicle under £10,000
- Supply Only£3,500 – £5,500
- Fitted (Indie)£4,300 – £6,700
- Warranty12–24 months
- Best ForMost owners — best cost/warranty balance
- Supply Only£4,500 – £6,500
- Fitted (Indie)£5,300 – £7,700
- Warranty12–24 months
- Best ForLong-term ownership; 3+ year horizon
- Supply Only£8,000 – £12,000
- Fitted (Indie)£9,500 – £14,000
- Warranty24–36 months
- Best ForInsurance jobs, warranty claims
Figures above reflect current Z4 replacement costs. The B48 variant typically sits at the higher end of the range. See the Era Map above for generation-specific pricing.
Labour estimate: Fitting a Z4 engine typically takes 10–14 hours at £65–£95/hr (independent) or £110–£160/hr (London/SE dealer).
Common Problems With BMW Z4 sDrive18i / sDrive20i Engines
2. B48 Oil Filter Housing & Coolant Leaks(G29)
3. VANOS Solenoid Failure(N20 & B48)
Ready to Compare?
Get Matched With a Vetted BMW Specialist
20+ vetted BMW specialists, every Z4 sDrive18i / sDrive20i variant covered, with a 12-month warranty as standard.
Z4 sDrive18i / sDrive20i — 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 |
|---|---|---|---|
| Timing chain rattle (N20 — preventative) | Yes | £1,500 – £3,000 | Essential maintenance — catch it before catastrophic failure |
| Snapped timing chain (N20) | Usually No | Engine replacement | Piston-valve contact means little is left to repair |
| B48 oil filter housing leak | Yes | £300 – £800 | Straightforward gasket replacement — prevent belt damage |
| B48 coolant leak (water pump/thermostat) | Yes | £400 – £900 | Catch it early — before overheating |
| VANOS solenoid failure | Yes | £300 – £800 | Proactive maintenance — restores performance |
| Carbon buildup (intake valves — direct injection) | Yes | £400 – £800 | Periodic cleaning — restores performance |
ProblemRepairable? · Typical Cost
Timing chain rattle (N20 — preventative)
Yes£1,500 – £3,000
Essential maintenance — catch it before catastrophic failure
Snapped timing chain (N20)
Usually NoEngine replacement
Piston-valve contact means little is left to repair
B48 oil filter housing leak
Yes£300 – £800
Straightforward gasket replacement — prevent belt damage
B48 coolant leak (water pump/thermostat)
Yes£400 – £900
Catch it early — before overheating
VANOS solenoid failure
Yes£300 – £800
Proactive maintenance — restores performance
Carbon buildup (intake valves — direct injection)
Yes£400 – £800
Periodic cleaning — restores performance
Buying This Z4 sDrive18i / sDrive20i? Check These First
Buy if:
- G29 (2018+) with the B48 engine (improved timing chain design)
- Post-2015 E89 with documented timing chain guide replacement
- Full service history with regular oil changes (critical for chain longevity)
- No cold-start rattling (timing chain health)
- No oil leaks around the oil filter housing (B48 — belt damage risk)
Avoid if:
- Pre-2015 E89 with cold-start rattle and no chain history — assume it's overdue
- No service history — the N20 is unforgiving of neglect
- Oil leaks around the oil filter housing (belt damage risk — B48)
- Overheating history or unexplained coolant loss — cooling system may be compromised
- VANOS system failure symptoms — loss of power, rough idle
Closing verdict
The Z4 sDrive18i / sDrive20i is BMW's entry-level turbocharged petrol roadster — powered by a 2.0-litre four-cylinder engine across two generations. The E89 (2009–2016) has the N20 — with well-known timing chain guide issues, particularly pre-2015. The G29 (2018+) has the B48 — a significant improvement with the timing chain design resolved. Common B48 issues are oil leaks, coolant leaks, and a starter motor recall on early models. With typical Z4 values ranging from £8,000 (E89) to £25,000+ (G29), an engine replacement is a significant investment — the B48-engined G29 is the safer choice.
Don’t Guess. Compare.
Get real quotes from vetted UK specialists and make the right call for your Z4 sDrive18i / sDrive20i.
- 20+ Vetted SpecialistsUK Network
- 12-Month Warrantyas Standard
- Nationwide Delivery& Collection
- Transparent PricingNo Hidden Fees
- Thousands of Z4 sDrive18i / sDrive20iOwners Helped
Buying Checklist
Before you buy a used BMW Z4 sDrive18i / sDrive20i (or before you commit to an engine replacement), check these:
1. Cold Start
Listen for rattling (N20 timing chain warning) — see the map above
2. Service History
Including which engine era (N20 or B48) and oil-change discipline
3. Timing Chain
For E89 N20: check for any chain work or cold-start rattle; pre-2015 most at risk
4. Oil Leaks
Check around oil filter housing (B48 — belt damage risk)
5. Coolant Level
Check reservoir when cold; any low or loss may indicate water pump or thermostat issues
6. VANOS Health
Test acceleration; any loss of power or sluggish response may indicate VANOS solenoid wear
7. Engine Warning Light
Have codes read; unresolved issues may indicate timing, cooling or sensor problems
8. MOT History
Check for emissions-related failures
Buying Checklist
Before you buy a used BMW Z4 sDrive18i / sDrive20i (or before you commit to an engine replacement), check these:
- 1
Cold Start
Listen for rattling (N20 timing chain warning) — see the map above
- 2
Service History
Including which engine era (N20 or B48) and oil-change discipline
- 3
Timing Chain
For E89 N20: check for any chain work or cold-start rattle; pre-2015 most at risk
- 4
Oil Leaks
Check around oil filter housing (B48 — belt damage risk)
- 5
Coolant Level
Check reservoir when cold; any low or loss may indicate water pump or thermostat issues
- 6
VANOS Health
Test acceleration; any loss of power or sluggish response may indicate VANOS solenoid wear
- 7
Engine Warning Light
Have codes read; unresolved issues may indicate timing, cooling or sensor problems
- 8
MOT History
Check for emissions-related failures
Buy smart. Drive with confidence.
A few checks today can save thousands tomorrow. Use this checklist to avoid the most common Z4 sDrive18i / sDrive20i pitfalls.
Engine Codes
This table's rows match Section 1B's Era Map exactly.
N20B20A
- Years
- 2009–2016 (E89)
- Power
- 156–184 bhp @ 5,000rpm
- 2025 Enquiries
- —(within N20 family volume)
- Avg. Recon Cost
- £3,500–£5,500[PLACEHOLDER]
B48B20A / B48B20B
- Years
- 2018–present (G29)
- Power
- 184–197 bhp @ 5,000rpm
- 2025 Enquiries
- —(within B48 family volume)
- Avg. Recon Cost
- £4,000–£6,500[PLACEHOLDER]
Technical SpecsB48B20A — G29 generation
- Displacement
- 1,997cc
- Cylinders
- 4-cylinder inline
- Compression Ratio
- 10.0:1
- Fuel System
- Direct injection, twin-scroll turbocharger
- Valves
- 16 valves, DOHC VVT
- Torque
- 270–290 Nm @ 1,250–4,500 rpm
- Displacement
- 1,998cc
- Cylinders
- 4-cylinder inline
- Compression Ratio
- 10.2:1–11.0:1
- Fuel System
- Direct injection, turbocharged
- Torque
- 300–320 Nm @ 1,250 rpm
Market Intelligence
Real data from thousands of Z4 sDrive18i / sDrive20i enquiries in 2025.
Most Common FailureN20 timing chain guide failure (E89 pre-2015)
The defining issue of the earlier Z4
Average Enquiry Mileage
50,000–70,000
miles
[PATTERN DATA]Average Replacement Cost
£4,000–£5,000
reconditioned, supply only
[PLACEHOLDER]Most Requested Engine Code
N20B20A / B48B20A
[PATTERN DATA]Peak Enquiry Season
Winter
Cold starts expose timing chain wear
[PATTERN DATA]Regional Demand
- South East
- 18%
- North West
- 16%
- Midlands
- 14%
- Other Regions
- 52%
Regional Demand Breakdown
14%Midlands18%South East16%North West52%Other Regions
Frequently Asked Questions
A reconditioned Z4 engine typically costs £3,500–£5,500 supply only, with the B48 variant at the higher end. Fitting adds £800–£1,300 depending on the specialist. A full engine replacement from a main dealer can cost £9,000–£13,000. Used engines can be found from £800–£2,000. Use our calculator for a figure specific to your Z4.
It depends on which engine era your Z4 has. The E89 (2009–2016) with the N20 has timing chain guide issues — the plastic guides can become brittle and deteriorate, causing excessive chain slack. Pre-2015 units are most at risk. The G29 (2018+) with the B48 is significantly more reliable — the timing chain design was improved. Common B48 issues include oil leaks from the oil filter housing, coolant leaks, and a starter motor recall on early models.
N20 timing chain guide failure (E89 pre-2015) — rattling on cold start is the warning sign. B48 oil filter housing oil leaks and water pump/thermostat coolant leaks (G29). VANOS solenoid failure on both engines. Carbon buildup on intake valves due to direct injection. The B48 is a significant improvement over the N20.
Depends on vehicle value and engine era. Against a well-kept G29 worth £18,000–£25,000, a £4,000–£5,000 recon is 15–25% of the car's value — worth it. Against a tired E89 worth £5,000–£10,000, the same recon may approach our 70% BMW threshold — get a scrap valuation first. B48-engined cars command a premium due to improved reliability.
E89 (2009–2016): N20B20A. G29 (2018–present): B48B20A or B48B20B. Check the VIN plate or vehicle documentation.
The chain guides must be replaced — they are the weak point. A preventative replacement of the timing chain and guides costs £1,500–£3,000. A snapped chain almost always destroys the engine, requiring a £3,500–£5,500+ replacement. At the first sign of cold-start rattle, book an inspection immediately. The B48 has far fewer timing chain issues — but regular oil changes remain essential.
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 condition, 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 sDrive18i / sDrive20i Owners Trust BMWEngines.uk
Trusted Z4 Engine Suppliers
every garage and engine rebuilder in our network is vetted, rated and reviewed by real Z4 sDrive18i and sDrive20i owners, as part of the Engine Finders network, across every generation — N20 and B48 — covering the E89 and G29 chassis.
Compare Z4 Engine Replacement Companies
see prices, warranty terms and supply & fit options side-by-side before you commit. We cover the 2.0-litre turbocharged petrol specifically, with specialists who understand the N20 timing chain vulnerabilities, B48 oil leak tendencies, and the unique requirements of the Z4 roadster.
UK Engine Replacement Services for Z4
supply-only or full supply & fit available nationwide, covering every generation of this badge since 2009, with a 12-month warranty as standard across our network.
Find the best BMW Z4 sDrive18i / sDrive20i engine replacement UK drivers rely on.
Compare prices from trusted specialists on EnginesMarket today and get your roadster back on the road with confidence.