How much does a BMW 1 Series 120i engine replacement cost in the UK?

A reconditioned BMW 1 Series 120i engine costs £2,500–£5,000 supply only, varying by generation: N46 £1,800–£3,000, N43 £2,200–£3,800, N13 £2,500–£4,200, B48 £3,500–£6,500. Fitting adds £900–£1,500. Check the Era Map above for your engine code.

Is the BMW 1 Series 120i reliable?

That depends on which engine your 120i has. The N46 is a robust but ageing naturally aspirated unit; the N43 adds direct-injection complexity; the N13 (Prince engine) has timing chain and HPFP issues pre-2015; the B48 is BMW's most refined and reliable four-cylinder. F40-generation (B48) is the best bet.

What are the common problems with the BMW 1 Series 120i?

N13: timing chain tensioner (cold-start rattle, £800–£1,500) and HPFP failure (long cranking, £600–£1,200). N43: NOx sensor failure (engine light, emissions, £400–£1,000). B48: coolant leaks and water pump issues (£400–£800). N46: VANOS seals and coil packs (£300–£800).

Is it worth replacing a BMW 1 Series 120i engine, or should I scrap the car?

1 Series values range from £2,000–£25,000 depending on generation, condition and mileage. A £2,500–£5,000 reconditioned engine represents 20–80% of vehicle value - our 70% BMW scrap threshold means careful evaluation is required. For a well-maintained F40, replacement is often justified. For an ageing E8x with other issues, assess scrap value first.

How do I find my BMW 1 Series 120i engine code?

The 120i has used four different engines: N46B20 (2004–2007, 150bhp), N43B20 (2007–2011, 170bhp), N13B16 (2011–2019, 170–184bhp), and B48B20 (2019–present, 184–190bhp). Check your VIN or registration year. The code is stamped on the engine block.

Can I repair the N13 timing chain issue, or does it need replacement?

Yes - if caught early. Timing chain and tensioner replacement costs £800–£1,500 and is significantly cheaper than a full engine replacement (£2,200–£4,200). The job requires specialist knowledge of the Prince engine. At the first sign of cold-start rattle, book an inspection immediately - ignored chain wear can lead to catastrophic piston-valve contact.

BMW 1 Series 120i2004–presentThree Engine Generations

BMW 1 Series 120i Engine Replacement — Compare Prices & Get Quotes

Name: BMW 1 Series 120i UK Engine Enquiry Data 2025
Creator: BMWEngines.uk

Get quotes today from trusted UK BMW specialists. The 120i badge spans naturally aspirated N46/N43, turbo N13 and modern B48 engines - compare reconditioned, rebuilt and used units with supply & fit available nationwide.

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BMW 1 Series 120i Engines - from £1,200 to £6,500Codes: N46B20, N43B20, N13B16, B48B20

BMW 1 Series 120i Engines - from £1,200 to £6,500· Codes: N46B20, N43B20, N13B16, B48B20

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BMW 1 Series 120i - Which Engine Does Your Car Actually Have?

Four generations. Four eras. One guide to reliability, costs and what really matters.

Era Note

Early 150bhp - proven chain-drive four, solid but ageing

GenerationYearsEngine CodeReliabilityRecon CostEra Note

E81/E87/E88 BMW 320d E81/E87/E88

2004–2007N46B20 (2.0L naturally aspirated)★★★★☆ [NEWLY ASSIGNED - see Data Note]£1,500–£3,000 [PLACEHOLDER - confirm vs cost sheet]Early 150bhp - proven chain-drive four, solid but ageing

E81/E87/E88 BMW 320d E81/E87/E88

2007–2011N43B20 (2.0L direct-injection)★★★½☆ [NEWLY ASSIGNED - see Data Note]£1,800–£3,500 [PLACEHOLDER - confirm vs cost sheet]170bhp DI variant - NOx system and injectors need monitoring

F20/F21

2011–2019N13B16 (1.6L turbo)★★★☆☆ [NEWLY ASSIGNED - see Data Note]£2,200–£4,200 [PLACEHOLDER - confirm vs cost sheet]Prince engine - timing chain and HPFP are key watchpoints

F40

2019–presentB48B20 (2.0L turbo)★★★★☆ [NEWLY ASSIGNED - see Data Note]£3,500–£6,500 [PLACEHOLDER - confirm vs cost sheet]Modern twin-scroll - well-developed, chain front-mounted

Why use this era map?

This table is the single source every other section on this page matches - Sections 2, 4 and 6 reference it rather than restating conflicting figures.

Real UK Cost Data

Verified Reliability

Expert Insights

Updated for 2025

BMW 1 Series 120i Engine Replacement Costs

Supply Only£2,500–£5,000

Fitted (Indie)£3,400–£6,200

Warranty12–24 months

Best ForMost owners - best cost/warranty balance

Engine TypeSupply OnlyFitted (Indie)WarrantyBest For

Used Engine£1,200–£3,500£2,100–£4,7001–6 monthsBudget priority; older E8x/F2x donors

Reconditioned Engine£2,500–£5,000£3,400–£6,20012–24 monthsMost owners - best cost/warranty balance

Rebuilt Engine£3,500–£6,500£4,400–£7,70012–24 monthsLong-term ownership; 5+ year horizon

Main Dealer New£6,000–£10,000£7,500–£11,50024–36 monthsInsurance jobs, warranty claims

Figures above reflect the current B48 generation. Older generations: see the Era Map above for N46/N43/N13-specific pricing, which runs lower on the used market.

Labour estimate: Fitting a 1 Series 120i engine typically takes 8–14 hours at £65–£95/hr (independent BMW specialist) or £110–£160/hr (London/SE dealer). The N13's turbo adds complexity vs N46/N43.

→ Compare BMW 1 Series 120i engine prices from UK specialists

Common Problems With BMW 320d Engines

1. Timing Chain Tensioner Failure (N13 - Pre-2015)

2. High-Pressure Fuel Pump (HPFP) Failure (N13)

3. NOx Sensor / Catalyst Issues (<a href='https://bmwengines.uk/engine/n40-n42-n43-n45-n46'>N43</a> - Direct Injection)

4. Coolant Leaks / Water Pump Failure (B48 - Modern)

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BMW 1 Series 120i - Repair, Buy, or Replace?

Every 320d has a story. Make the right call with clear data, real-world costs, and honest guidance from UK specialists.

BMW 1 Series 120i - Repair, Buy, or Replace?

Every 320d has a story. Make the right call with clear data, real-world costs, and honest guidance from UK specialists.

Can It Be Repaired?

ProblemRepairable?Typical CostWhen It Makes SenseN13 timing chain tensioner✅ Yes£800–£1,500Preventative - catches the fault before catastrophic failureN13 HPFP failure✅ Yes£600–£1,200Straightforward repair on an otherwise healthy engineN43 NOx sensor failure✅ Yes£400–£1,000Viable - MOT pass depends on NOx/emissions complianceN46 coil packs / VANOS seals✅ Yes£300–£800Simple, low-cost maintenance itemsMajor internal failure (any)❌ Usually NoEngine replacement requiredAssess vehicle value carefully - see scrap threshold

Buying This BMW 1 Series 120i? Check These First

Buy If

F40-generation B48 (2019+) - the most reliable 120i by a margin
N13 (F20) post-2015 with timing chain history and HPFP replaced
N46 with documented VANOS seal and coil pack history
Full service history with correct oil specification for the era

Avoid If

N13 pre-2015 with no timing chain history - the risk is real
N43 with emissions warning light and no diagnosis (NOx sensor likely)
Any 120i with poor service history - all engines are unforgiving of neglect
E8x N46 with no VANOS history - simple to fix but suggests neglect

Closing Verdict

The 120i is a badge that spans 20 years of BMW four-cylinder engineering, from the robust but ageing N46 to the sophisticated B48. The F40 B48 is the most reliable, the N13 is the most temperamental (but can be made reliable), and the N46 remains a solid budget choice if maintained. Buy on history, maintain the chain/HPFP on the N13, and the 120i will serve you well.

Don't guess.Get the right engine at the right price.

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Buying Checklist

Before you buy a used BMW 1 Series 120i (or before you commit to an engine replacement), check these:

Cold Start

Any rattle? N13 chain rattle is metallic; N46/N43 should be quiet

Service History

Check the year to identify which engine - pre-2007 N46, 2007-2011 N43, 2011-2019 N13, 2019+ B48

Timing Chain History

N13 (pre-2015): chains replaced? Tensioner checked?

High-Pressure Fuel Pump

N13: has HPFP been replaced? Long cranking is a warning

Emissions / NOx

N43: any engine light? NOx sensor is common

VANOS Operation

N46: check low-end power; VANOS seals degrade

Coolant Level

B48: any loss? Water pump and connections are key risks

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 320d pitfalls.

Buy smart. Drive with confidence.

A few checks today can save thousands tomorrow. Use this checklist to avoid the most common 320d pitfalls.

BMW 320d Engine Codes

This table's rows match Section 1B's Era Map exactly.

N46B20 (2.0L naturally aspirated)

Years2004–2007

Power150 bhp

2025 Enquiries- (pattern data - heritage)

Avg. Recon Cost£1,800–£3,000 [PLACEHOLDER]

Engine CodeYearsPower2025 EnquiriesAvg. Recon Cost

N46B20 (2.0L naturally aspirated)2004–2007150 bhp- (pattern data - heritage)£1,800–£3,000 [PLACEHOLDER]

N43B20 (2.0L direct-injection)2007–2011170 bhp- (pattern data - heritage)£2,200–£3,800 [PLACEHOLDER]

N13B16 (1.6L turbo)2011–2019170–184 bhp- (pattern data - high-volume UK)£2,500–£4,200 [PLACEHOLDER]

B48B20 (2.0L turbo)2019–present184–190 bhp- (pattern data - modern)£3,500–£6,500 [PLACEHOLDER]

Technical Specs

B48B20

Displacement1,995 cc

Cylinders4-cylinder inline

Compression Ratio10.0:1

Fuel SystemMulti-point injection (MPI)

TurbochargerNaturally aspirated

Displacement1,995 cc

Cylinders4-cylinder inline

Compression Ratio12.0:1

Fuel SystemDirect injection

TurbochargerNaturally aspirated

Displacement1,598 cc

Cylinders4-cylinder inline

Compression Ratio10.5:1

Fuel SystemDirect injection

TurbochargerSingle twin-scroll

Displacement1,998 cc

Cylinders4-cylinder inline

Compression Ratio10.2:1

Fuel SystemDirect injection

TurbochargerSingle twin-scroll

→ Compare BMW 1 Series 120i engine prices for your BMW

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Market Intelligence

Most Common Failure

N13: timing chain tensioner (~55% of N13 enquiries) / B48: coolant leaks (~35% of B48 enquiries)

[PATTERN DATA - specialist workshop consensus]

Average Enquiry Mileage

65,000

miles

[PATTERN DATA]

Average Replacement Cost

£4,000

reconditioned (B48 era), supply only

[PLACEHOLDER - confirm vs cost sheet]

Most Requested Engine Code

N13B16 (F20 120i is the highest-volume UK variant)

[PATTERN DATA]

Peak Enquiry Season

Autumn/Winter

cold starts expose chain issues; cooling systems leak when cold

[PATTERN DATA]

Regional Demand

South East22%

London18%

North West15%

PATTERN DATA

Regional Demand Breakdown

22%South East

18%London

15%North West

BMW 320d - Frequently Asked Questions

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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see prices, warranty terms and supply & fit options side‑by‑side before you commit, with transparent pricing for every 120i era from E8x to F40.
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As standard

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