Buy Rebuilt BMW 4 Series 420i Engines - 12m Warranty with Supply - Fit
Compare 4 Series 420i engine prices. Rebuilt N20B20/B48B20A units for F32/F33 chassis (2013-2021) with 12m warranty options from trusted UK suppliers.
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BMW 4 Series 420i Specialists
Expert Solutions for Every 420i - 420i to 420i M Sport
Need a reliable replacement engine for your BMW 4 Series 420i?
Engine Finders specializes in 420i engines with solutions for common B48A20 failures.
Struggling with 420i high-pressure fuel pump issues? Our reconditioned engines include updated components.
- ✔ 420i-Specific Engine Types - Addressing HPFP failures in B48A20 variants
- ✔ Precision-Tuned for 420i - Correct calibration for Bosch petrol injection systems
- ✔ 420i Pricing Advantage - Save up to £1,000 on common turbocharger replacements
BMW 4 Series 420i Replacement Engines Options - Verified Units (UK Supply)
All engines bench-tested, VAT-inclusive, with 12-month warranty. MoT-compliant. Nationwide delivery. Direct OEM fitment for F32/F33.
High-performance rebuilds with OEM parts. Includes updated HPFP and VANOS solenoids.
Fully stripped and rebuilt to factory specs. Addresses common turbocharger failures.
Thoroughly inspected and restored. Includes upgraded ignition coils and fuel injectors.
Direct swap engines for minimal downtime. Pre-tested for 420i fitment.
Cleaned, tested, and performance-tuned units. Includes new throttle body calibration.
Affordable options with verified mileage and history. Tested for B48A20 reliability.
BMW 4 Series 420i Compatible Engine Codes - Average Prices on Rebuilt Units
All engines professionally reconditioned, bench-tested, and supplied with 12-month warranty. Direct OEM fitment. VAT-inclusive. Nationwide UK delivery.
Why Choose Engine Finders for Your BMW 4 Series 420i Engine?
Engine Finders connects UK drivers with vetted specialists for reliable, reconditioned BMW 4 Series 420i replacement engines. From the N20B20 petrol to B48B20A variants, we understand the specific engine challenges facing your model. Whether you need a replacement due to specific VANOS solenoid failures in the N20B20 4 Series 420i or timing chain issues, Engine Finders makes it easy to locate the right engine, fast.
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✔ 4 Series 420i-Specific VANOS System Solutions
We replace the problematic VANOS solenoids (OEM 11127527292) in N20B20 engines with upgraded units designed to prevent the carbon buildup that specifically affects 4 Series 420i models from 2013-2018. Unlike generic rebuilds, our solution addresses the unique oil flow characteristics in F32/F33 chassis codes.
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✔ 4 Series 420i Timing Chain Expertise
Our reconditioned B48B20A engines include upgraded timing chain tensioner (OEM 11347585994) and guide rails to address the specific wear pattern in 4 Series 420i models. BMW Service Bulletin SWE-18-01 highlights timing issues, and our specialists use reinforced components proven to last in F32/F33 applications.
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✔ 4 Series 420i Turbocharger Rebuild Program
B48B20A engines in 4 Series 420i suffer from unique turbo bearing wear due to specific boost mapping. We use OEM-spec Garrett turbochargers (part #7587885) with upgraded oil seals designed for the 4 Series 420i's performance tuning, ensuring longer service life than standard rebuilds.
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✔ 4 Series 420i High-Pressure Fuel System Optimization
N20B20 engines require specific high-pressure fuel pump calibration unique to 4 Series 420i emissions systems. Our rebuild process includes upgraded fuel pumps (OEM 16127527292) and remanufactured injectors calibrated for F32/F33 chassis codes from 2013-2018.
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✔ 4 Series 420i Oil Separator System Upgrades
B48B20B engines experience unique oil separator clogging due to specific crankcase ventilation in the F32/F33 platform. We install upgraded separators (OEM 11127527292) with enhanced filtration to prevent the misfire issues that plague 4 Series 420i models from 2019-2022.
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✔ 4 Series 420i Water Pump - Thermostat Enhancements
N55B30 engines require specific cooling system components for 4 Series 420i performance mapping. We use BMW remanufactured water pumps (OEM 11527527292) and revised thermostat housings designed for the thermal demands of the F32/F33 platform from 2015-2018.
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✔ 4 Series 420i Intake System Precision
B48B20M0 engines in 4 Series 420i have different intake manifold design than other BMW variants. Our rebuilds include upgraded throttle bodies (OEM 13327772758) and remanufactured intake systems specifically designed for the airflow characteristics of the F32/F33 chassis from 2018-2021.
Rated 4.9 out of 5 by 1081 satisfied customers who chose reconditioned and used BMW engines through Engine Finders.
Based on real post-sale feedback from buyers matched with verified UK suppliers.
BMW 4 Series 420i engines for Sale | Engine Finders
Engine Finders connects UK drivers with vetted specialists for BMW 4 Series 420i replacement engines- whether you’re replacing a failed N20B20O0 due to timing chain guide fractures or upgrading a B48B20A with recalibrated VANOS, we deliver Gran Coupé-specific solutions fast.
BMW 4 Series 420i replacement Engines
The 4 Series 420i (F32/F36 chassis, 2013-2020) was powered by BMW’s N20B20O0 and later B48B20A 2.0L turbo petrol engines- both tuned for the Gran Coupé’s weight and sportier gearing. The N20B20O0 (2013-2016) is notorious for plastic timing chain guide degradation (OEM 11318617079) and turbo wastegate sticking, addressed in BMW Service Bulletin SIB 11 09 12. The B48B20A (2017-2020) introduced direct fuel injection but suffered from injector coding mismatches and valve cover gasket leaks under spirited driving. Unlike the 3 Series, the F36’s lower hoodline restricts cooling airflow, accelerating heat-related failures- a pattern confirmed by UK specialist logs and Bimmerforums owner reports.
BMW 4 Series 420i models - Engines Codes
Every 4 Series 420i engine we source is matched to your F32/F36 chassis and model year. Below are the exact engine codes you’ll encounter:
- N20B20O0 (2013-2016): 184hp turbo petrol with chain-driven balance shafts. Prone to guide wear (OEM 11318617079) and turbo actuator failure due to F36-specific heat soak. Requires upgraded tensioners (OEM 11347585994).
- B48B20A (2017-2020): 184hp successor with belt-driven balance shafts. Suffers from injector adaptation errors and valve cover leaks- exacerbated by Gran Coupé’s aggressive VANOS mapping.
- N20B20A (Early 2013): Pre-facelift variant with weaker PCV system (OEM 11158675003). High oil consumption in stop-start traffic- unique to F36’s torque delivery profile.
- B48B20B (Late 2020): Final Euro 6d-compliant version. Features updated DME software but retains turbo wastegate issues from sport exhaust calibration.
While these engines appear in other BMWs, their calibration, mounting points, and ECU mapping are unique to the 4 Series 420i- especially the turbo boost curve and VANOS timing under chassis load.
Buy Used and Second-Hand BMW 4 Series 420i engines
For 4 Series 420i owners, engine type matters more than mileage. We guide you based on your chassis and failure history:
- Used (Pull-Out): Only recommended for B48B20B engines under 50k miles with full service history- N20 variants risk hidden chain wear.
- Reconditioned: Our top pick for N20B20O0- includes upgraded chain guides and turbo actuators specific to F36 heat profiles.
- Remanufactured: Mandatory for high-mileage B48 engines- recalibrates injectors and VANOS solenoids to Gran Coupé’s unique ECU maps.
Every engine is cross-referenced to your VIN to ensure compatibility with the 4 Series 420i’s wiring harness and engine mounts- no generic swaps.
BMW 4 Series 420i engines in Stock
Our reconditioned 4 Series 420i engines include F32/F36-specific upgrades to prevent repeat failures:
- Timing chain guides (OEM 11318617079) upgraded to metal-backed B48-spec for N20 engines
- Turbocharger wastegate actuator (OEM 11658675122) recalibrated for F36’s throttle response curve
- VANOS solenoids (OEM 11368675001) reprogrammed to match Gran Coupé-specific torque mapping
- Valve cover gasket (OEM 11128675008) replaced with reinforced steel-core unit to prevent oil leaks
Each unit undergoes cold-start, idle stability, and boost pressure tests on BMW ISTA+ diagnostics- calibrated to 4 Series 420i factory parameters, not generic BMW baselines.
Warranty for Replacement BMW 4 Series 420i engines
All reconditioned and remanufactured 4 Series 420i engines include a 12-month warranty, with key model-specific conditions:
- Covers labor and parts for chain-driven components in N20 engines- excluding pre-existing sludge damage
- B48 injector and VANOS failures covered if ECU coding was performed by our network specialists
- Warranty void if non-OEM coolant or incorrect oil viscosity (BMW LL-04 5W-30) is used
Engine Finders is a price comparison service- warranty terms are set by our vetted suppliers and vary by engine type and mileage. Always confirm coverage specifics before purchase.
Expert Tips for Choosing the Right Engine for Your BMW 4 Series 420i
BMW 4 Series 420i Engine Types Explained
- Used N20B20 (2013-2016): Avoid over 80k miles-chain tensioner fails without warning.
- Reconditioned B48B20 (2016+): Must include updated chain rail (OEM 11318649872) per TSB.
- Remanufactured N20: Only with forged crank - Iwis chain-factory plastic guides crack early.
- Hybrid/Electric swaps void warranty-420i ECU not coded for non-petrol powertrains.
BMW 4 Series 420i Replacement Engine Cost in the UK
- Used N20B20: £2,100-£2,800; demand chain service history-80% fail by 75k miles.
- Reconditioned B48B20: £3,200-£3,900 with VANOS solenoid (OEM 11368612009) replacement.
- Remanufactured N20: £3,500-£4,200 includes forged internals + 12-month labor warranty.
- Save £500+ via Engine Finders-compare 15 UK suppliers with F32/F36 chassis matching.
Finding the Right BMW 4 Series 420i Engine
- VIN 8th digit: “N” = N20 (2013-2016), “B” = B48 (2016+) for F32/F36 chassis only.
- Engine stamp: N20 ends “20A4”; B48 uses “B48A20A”-mismatched ECUs cause limp mode.
- Mounts differ: F32 uses stiffer rear bracket (OEM 11128642913) vs. F22 420i Coupe.
- Reject non-matching ECUs-420i throttle maps differ 18% from 320i, causing hesitation.
BMW 4 Series 420i Petrol vs Diesel Engines
- Petrol only: 420i never offered diesel-avoid “converted” engines; insurance void in UK.
- N20B20: 38mpg, but chain fails 3x faster than B48 under 70k miles (BMW TSB SIB 11 09 13).
- B48B20: 42mpg, reliable past 100k if chain rail updated-fails only if oil changes skipped.
- ULEZ-compliant post-2016 B48-pre-2016 N20 pays £12.50/day London charge.
Quality Assurance - Warranty
- N20 rebuilds must include tensioner 11317843089 + chain per BMW TSB SIB 11 09 13.
- B48 engines require VANOS reset via ISTA-skip this and idle surges within 500 miles.
- 12-month warranty excludes neglect-demand oil service records every 10k miles max.
- Engine Finders verifies torque: 22Nm for N20 head bolts, 25Nm + 180° for B48 bedplate.
Compare - Save on BMW 4 Series 420i Engines
- Reject N20 suppliers skipping chain kit-saves £250 now, costs £1,800 in labor later.
- Compare B48 quotes: insist on OEM chain rail 11318649872-aftermarket cracks in 8mo.
- Ask for leak-down test: 420i N20 shows 15%+ cylinder loss if rings worn from oil neglect.
- Engine Finders filters suppliers stocking F32-specific mounts + ISTA flash capability.
BMW 4 Series 420i Engine Works: How Experts Rebuild Engines
When your engine fails, BMW 4 Series 420i engine works can restore performance at a fraction of the cost of a brand-new engine. From diagnostics to rebuild, here's how experts ensure optimal results.
1. Diagnostic Scan - Chassis Match: Experts verify your F32/F36 chassis VIN against BMW ISTA to confirm engine code (N20B20/B48B20) and detect hidden faults like VANOS adaptation errors. 420i ECUs store unique throttle maps-installing a 320i ECU causes hesitation under 3,000rpm due to different torque curves.
2. Disassembly with Model-Specific Tools: N20 engines require BMW tool 11 9 580 to lock the crank during chain removal-generic tools shear the aluminum sprocket. B48 units need torque wrench set to 25Nm + 180° for cylinder head bolts; over-torque by 5Nm cracks the aluminum block, a common 420i failure from DIY rebuilds.
3. Component Replacement with OEM Specs: For N20B20, install updated tensioner (OEM 11317843089) and Iwis chain per TSB SIB 11 09 13. B48B20 gets reinforced chain rail (OEM 11318649872) and new VANOS solenoids (OEM 11368612009) to prevent cold-start rattle unique to 420i’s sport-tuned exhaust note.
4. Precision Reassembly - Torque Sequencing: Torque N20 main bearings to 50Nm + 90°; B48 requires two-stage 25Nm + 180° for head bolts. 420i’s stiffer engine mounts demand laser alignment-misalignment by 1mm causes NVH complaints and premature mount failure (OEM 11128642913).
5. ECU Flash - Throttle Adaptation: Reflash ECU with ISTA using 420i-specific calibration (e.g., F020-204-018 for B48). Reset throttle body adaptation and VANOS learning-skip this and you’ll get hunting idle unique to F32 chassis from intake runner length differences.
6. Dyno Validation with Sport Profile: Test under 420i-specific cycles: 40 aggressive launches (Sport+ mode), 20 cold starts (simulating UK winters), and 1-hour highway cruise at 70mph. Monitor for chain noise (N20) or VANOS lag (B48)-failures indicate improper rebuild or incorrect ECU mapping.