Engines Market

BMW 120i SPECIALISTS

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

Get quotes today from trusted UK BMW 1 Series 120i engine specialists. Compare prices on reconditioned, rebuilt and used engines for your BMW 120i - covering the naturally aspirated N46 and N43 engines in the first-generation E8x cars, through to the turbocharged N13 and B48 units in the F20/F21 and F40 generations.

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BMW 1 Series 120i Engine
from£1,195 to £3,200
  • Usedfrom £750
  • Reconditionedfrom £1,195
  • Common codesN46B20B, N43B20O0, N13B16M0
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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 120i Engine History & Specs at a Glance

The BMW 120i has been a popular petrol model across three generations of the 1 Series in the UK, offering a step up in power from the 118i without the running costs of the six-cylinder 125i and 130i. Launched with the first-generation E87 in 2004, it has evolved from a naturally aspirated 2.0-litre four-cylinder to a 1.6-litre turbo, and finally to a modern 2.0-litre turbocharged B48 unit. The 120i badge represents the sweet spot between accessible performance and everyday usability.

BMW 1 Series 120i
  1. 2004

    N46B20B, 2.0L naturally aspirated I4, 150 hp, launched with the E87 five-door and E81 three-door 1 Series

  2. 2007

    N43B20O0, 2.0L naturally aspirated I4 with direct injection, 170 hp, introduced as part of the E87/E81 LCI update

  3. 2011

    N13B16M0, 1.6L turbocharged I4, 177 hp, launched with the second-generation F20/F21 1 Series

  4. 2016

    B48B20M0, 2.0L turbocharged I4, 184 hp, introduced as part of the F20/F21 LCI update

  5. 2019

    F40 generation launches with B48A20A, 2.0L turbocharged I4, 178 hp, continuing the 120i badge

  6. 2024

    Current F70 generation continues with updated B-series petrol engines

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

Engine Codes & Pricing

BMW 1 Series 120i Engine Codes Specifications & Replacement Cost

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

N46B20B — 2.0L Naturally Aspirated Petrol (2004-2007) engine

N46B20B — 2.0L Naturally Aspirated Petrol (2004-2007)

Power Output
150 hp (110 kW)
Years Fitted
2004-2007

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

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

Common Problems

BMW 1 Series 120i Engine Problems Repair Cost vs Replacement

The BMW 1 Series 120i has been powered by five different petrol engines across its production life, each with its own character and weaknesses. Early cars (2004-2007) use the N46B20B - a 2.0-litre naturally aspirated unit that can suffer from timing chain wear and oil consumption. The N43B20O0 (2007-2011) introduced direct injection but brought timing chain guide fragmentation and multiple sensor issues. The N13 turbo (2011-2016) offered 177 hp but inherited timing chain problems from the Prince engine family. Later B48-powered cars (2016-present) are the most reliable of the bunch, with no widespread timing chain failure pattern. Replacement demand for the BMW 120i is driven primarily by N43 and N13 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 120i (N43B20O0 / N13B16M0, 2007-2016)
Typical failure mileage
40,000-100,000 miles (N43); 50,000-80,000 miles (N13)
Root cause
The timing chain guides on BMW's N43 and N13 petrol engines were made of plastic that becomes brittle with age and heat. On the N43, 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. On the N13, the timing chain is known to stretch and snap. Because both engines are of interference type, 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 or N13-powered BMW 120i, 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 120i for 2+ years, a reconditioned N43 or N13 with upgraded timing components and warranty offers genuine peace of mind.
-> Compare rebuilt N13B16M0 BMW 1 Series 120i engine prices

Oil Consumption & Valve Stem Seal Wear

Affected
BMW 1 Series 120i (N46B20B / N43B20O0, high-mileage examples)
Typical failure mileage
80,000-120,000 miles
Root cause
The N46 and N43 engines 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. The N46 in particular has been reported to use 1 litre of oil per 300 miles when the seals are badly worn.

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 120i. If combined with timing chain wear, a full rebuilt engine with upgraded components may offer better long-term value.
-> Compare rebuilt BMW 1 Series 120i engine prices

B48 Engine

Affected
BMW 1 Series 120i (B48B20M0 / B48A20A, 2016-present)
Typical failure mileage
40,000-100,000 miles
Root cause
The B48 is generally a reliable engine, but owners report coolant leaks, particularly from the coolant flange pipe. Carbon buildup on intake valves can occur due to direct injection, and some owners have reported cracked pistons in tuned examples. Widespread B48 timing chain failures are not a known pattern.

Repair options

Repair tierDealer priceSpecialist price
Coolant Leak Repair£300-£600£200-£400
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. Coolant leaks should be addressed promptly to prevent overheating. 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. If you're considering a remap, be aware that tuned B48 engines have been known to suffer from cracked pistons.
-> Compare rebuilt BMW 1 Series 120i B48 engine prices

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

The N43 and N13 engines in your BMW 120i have known timing chain weaknesses - but with the right specialist, these can be addressed before catastrophic failure occurs. Later B48-powered cars are more reliable but still benefit from regular maintenance and vigilance for coolant leaks. 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 120i inside out. Compare prices today and keep your BMW on the road.

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FAQ

BMW 1 Series 120i Engine ReplacementFrequently Asked Questions

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

Why Choose Us

Compare BMW 1 Series 120i Engine Prices Today

Comparing quotes for your BMW 1 Series 120i 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, N13 and B48 petrol engines inside out. No spam, no pressure, just genuine prices from trusted BMW 120i experts.

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