Engines Market

BMW 120 SPECIALISTS

BMW 1 Series 120 Engine Replacement Compare Prices & Get Quotes

Get quotes today from trusted UK BMW 1 Series 120 specialists. Compare prices on reconditioned, rebuilt and used engines for your BMW 120 - covering the 2.0-litre N46 and N43 naturally aspirated petrol engines in the first-generation E8x cars, through to the modern B48 turbocharged units in the F40 and F70 generations.

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BMW 1 Series 120 Engine
from£1,195 to £3,500
  • Usedfrom £750
  • Reconditionedfrom £1,195
  • Common codesN46B20B, N43B20A, B48A20A
BMW 1-series 120 Used Engine — N46B20BBMW 1-seriesUsed Engine — N46B20BBMW 1-series 120 Reconditioned Engine — N46B20BBMW 1-seriesReconditioned Engine — N46B20BBMW 1-series 120 Rebuilt Engine — N46B20BBMW 1-seriesRebuilt Engine — N46B20B

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How it works

3 Simple Steps to Finding the Right Replacement Engine

Clear information first, then the right engine and specialist for your exact vehicle.

Variant History

BMW 1 Series 120 Engine History & Specs at a Glance

The BMW 120 has been a core petrol model across multiple generations of the 1 Series in the UK, offering the sweet spot between accessible performance and everyday usability. Launched with the first-generation E87 in 2004 as the 120i, it has evolved from a naturally aspirated 2.0-litre four-cylinder to a modern turbocharged B48 unit.

BMW 1 Series 120
  1. 2004

    N46B20B, 2.0L naturally aspirated I4, 150 hp (110 kW), launched with the E87 five-door 1 Series

  2. 2006

    N43B20A, 2.0L naturally aspirated I4 with direct injection, 170 hp (125 kW), introduced with the E87 LCI update

  3. 2019

    F40 generation launches with B48A20A, 2.0L turbocharged I4, 178 hp (130 kW), replacing the 120i badge with 120

  4. 2024

    Current F70 generation continues with updated B48 petrol engines, now badged as 120

Every engine fitted to the BMW 1 Series 120 is covered below, with UK rebuilt pricing and known failure points.

Engine Codes & Pricing

BMW 1 Series 120 Engine Codes Specifications & Replacement Cost

Find your exact engine code, specs and UK replacement cost guide.

N46B20B — 2.0L Naturally Aspirated Petrol (2004-2006) engine

N46B20B — 2.0L Naturally Aspirated Petrol (2004-2006)

Power Output
150 hp (110 kW)
Years Fitted
2004-2006

Can’t find your exact engine code?-> Get quotes for N46B20B BMW 1 Series 120 engine replacement

-> Get quotes for N46B20B BMW 1 Series 120 engine replacement

Common Problems

BMW 1 Series 120 Engine Problems Repair Cost vs Replacement

The BMW 1 Series 120 has been powered by three different petrol engines across its production life. Early cars (2004-2006) use the N46B20B - a 2.0-litre naturally aspirated unit that can suffer from timing chain wear and oil consumption. The N43B20A (2006-2011) introduced direct injection but brought timing chain guide fragmentation and multiple sensor issues. Modern B48-powered cars (2019-present) are the most reliable of the bunch. Replacement demand for the BMW 120 is driven primarily by N43 timing chain failure. Every rebuilt engine supplied through EnginesMarket includes upgraded components addressing the original failure points, plus a minimum 12-month unlimited-mileage warranty.

Common failure points and repair options

Timing Chain Guide Failure

Affected
BMW 1 Series 120 (N43B20A, 2006-2011)
Typical failure mileage
40,000-100,000 miles
Root cause
The timing chain guides on BMW's N43 petrol engine were made of plastic that becomes brittle with age and heat. The guides can break and fragment, with debris falling into the sump and blocking the oil pump intake - leading to oil starvation and engine seizure. Because the N43 is an interference engine, a stretched or snapped timing chain can cause pistons to collide with valves - resulting in catastrophic engine failure.

Repair options

Repair tierDealer priceSpecialist price
Timing Chain Replacement (preventative)£1,200-£1,800£800-£1,300
Full Replacement - rebuilt/reconditioned engine£3,200-£4,800£2,300-£3,800 (matches Section 4 rebuilt pricing)
Our recommendation
If you hear the characteristic rattling noise from the timing chain on cold start in your N43-powered BMW 120, act immediately. An £800-£1,300 specialist timing chain replacement is far cheaper than a full engine rebuild. If the chain has already snapped, the repair bill often exceeds the car's value - in that scenario, compare rebuilt engine prices through EnginesMarket against the cost of replacing the car. For owners planning to keep their 120 for 2+ years, a reconditioned N43 with upgraded timing components and warranty offers genuine peace of mind.
-> Compare rebuilt N43B20A BMW 1 Series 120 engine prices

Oil Consumption & Valve Stem Seal Wear

Affected
BMW 1 Series 120 (N46B20B, high-mileage examples)
Typical failure mileage
80,000-120,000 miles
Root cause
The N46 engine can suffer from worn valve stem seals, leading to excessive oil consumption. This is often accompanied by blue smoke on start-up and a gradual increase in oil usage between services.

Repair options

Repair tierDealer priceSpecialist price
Valve Stem Seal Replacement£1,000-£1,500£700-£1,100
Full Replacement - rebuilt engine£3,200-£4,800£2,300-£3,800
Our recommendation
Oil consumption of 1 litre per 1,000 miles or more warrants investigation. A specialist valve stem seal replacement using the "in-situ" method (without cylinder head removal) is often the most cost-effective solution for the BMW 1 Series 120. If combined with timing chain wear, a full rebuilt engine with upgraded components may offer better long-term value.
-> Compare rebuilt BMW 1 Series 120 engine prices

B48 Engine

Affected
BMW 1 Series 120 (B48A20A, 2019-present)
Typical failure mileage
40,000-100,000 miles
Root cause
The B48 is generally a reliable engine, but like all direct-injection engines, carbon buildup on intake valves can occur over time. Cooling system components and the oil filter housing are known wear points.

Repair options

Repair tierDealer priceSpecialist price
Intake Valve Cleaning (Walnut Blasting)£500-£800£350-£600
Full Replacement - rebuilt engine£3,500-£5,000£2,500-£3,800
Our recommendation
The B48 is BMW's most advanced four-cylinder petrol engine and is generally reliable with proper maintenance. Carbon buildup is a maintenance issue rather than a catastrophic failure point - regular high-speed driving can help reduce deposits, but professional cleaning is sometimes necessary.
-> Compare rebuilt BMW 1 Series 120 B48 engine prices

Don't Let Engine Failure Write Off Your BMW 1 Series 120

The N43 engine in your BMW 120 has known timing chain weaknesses - but with the right specialist, these can be addressed before catastrophic failure occurs. Modern B48-powered cars are more reliable but still benefit from regular maintenance. Whether you need a preventative timing chain replacement or a full rebuilt engine with upgraded components and a 12-month warranty, EnginesMarket connects you with vetted UK specialists who know the 120 inside out. Compare prices today and keep your BMW on the road.

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FAQ

BMW 1 Series 120 Engine ReplacementFrequently Asked Questions

Everything BMW 1 Series 120 owners usually ask before choosing a rebuilt, reconditioned or used replacement engine.

Why Choose Us

Compare BMW 1 Series 120 Engine Prices Today

Comparing quotes for your BMW 1 Series 120 engine replacement is completely free and carries no obligation. Enter your registration above, tell us your preferred engine condition - used, reconditioned or rebuilt - and receive tailored quotes from vetted UK specialists who know the N46, N43 and B48 petrol engines inside out. No spam, no pressure, just genuine prices from trusted BMW 120 experts.

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