How much does a BMW 3 Series 320i engine replacement cost in the UK?

A reconditioned 320i engine typically costs £900–£7,500 supply only depending on generation. M10/M20-era engines sit at the lower end (£900–£2,500), while B48 units run £3,200–£7,500. Fitting adds £650–£1,500. Use our calculator for a figure specific to your car.

Is the BMW 3 Series 320i engine reliable?

It depends entirely on which of the ten engine generations your 320i has. The six-cylinder cars (E21–E46) are generally very reliable, with the M20 being one of BMW's most durable engines. The N43 (2007–2011) is widely considered one of the worst BMW engines ever made. The N20 has timing chain guide issues. The B48 (2015+) is a significant improvement. Check the Era Map above for your specific car.

What are the common problems with the BMW 3 Series 320i?

Timing chain failure on the N43 and N20, cooling system failures on E36/E46 six-cylinder cars, valve cover gasket leaks on the M54 and N46, and NOx sensor issues on the N43. The N43 is the most problematic - timing chain guides break up and debris blocks the oil pickup.

Is it worth replacing a BMW 3 Series 320i engine, or should I scrap the car?

Depends on vehicle value and generation. Against a well-kept £7,000 F30 320i, a £4,000 recon is 57% of the car's value - borderline. Against a tired £3,500 E90 example, the same recon exceeds our 70% BMW threshold - get a scrap valuation first. For B48-engined cars (post-2015), higher vehicle values make replacement more viable.

How do I find my BMW 3 Series 320i engine code?

Listed on the VIN plate and vehicle documentation. As a rule of thumb: E21 (1975–1982) is M10B20, E30 (1982–1991) is M20B20, E36 (1991–1998) is M50B20/M52B20, E46 (1998–2005) is M52TUB20/M54B22, E90 (2005–2011) is N46B20/N43B20, F30 (2012–2019) is N20B20/B48B20, G20 (2019–present) is B48B20. Tell us your registration date and we'll confirm it for free.

Can I repair the N43 timing chain, or does it need replacement?

Yes - if caught early. A preventative chain replacement (£800–£2,500) is far cheaper than a catastrophic chain snap requiring a full engine replacement. At the first sign of cold-start rattle, book an inspection immediately. Many specialists recommend preventative replacement at 60,000 miles regardless of symptoms on the N43.

BMW 3 Series 320i1975–present9 Engine Generations

BMW 3 Series 320i Engine Replacement — Compare Prices & Get Quotes

Name: BMW 3 Series 320i UK Engine Enquiry Data 2025
Creator: BMWEngines.uk

The 320i badge has defined the 3 Series for five decades - from the original four-cylinder M10 to the turbocharged B48. Get quotes from trusted UK BMW specialists for every era, supply & fit available nationwide.

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BMW 3 Series 320i Engines - from £900 to £7,500Common codes: M10B20, M20B20, M50B20, M52B20, M54B22, N46B20, N43B20, N20B20, B48B20

BMW 3 Series 320i Engines - from £900 to £7,500· Common codes: M10B20, M20B20, M50B20, M52B20, M54B22, N46B20, N43B20, N20B20, B48B20

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The 320i THROUGH TIME - Era Map

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

Era Note

Original fuel-injected 320i - robust but now rare and ageing

GenerationYearsEngine CodeReliabilityRecon CostEra Note

E21

1975–1982M10B20★★★★☆ [NEWLY ASSIGNED - see Data Note]£900–£2,200 [PLACEHOLDER - confirm vs cost sheet]Original fuel-injected 320i - robust but now rare and ageing

E30

1982–1991M20B20★★★★½ [NEWLY ASSIGNED - see Data Note]£1,000–£2,500 [PLACEHOLDER - confirm vs cost sheet]Silky-smooth six-cylinder - one of BMW's most durable engines

E36

1991–1998M50B20 / M52B20★★★★☆ [NEWLY ASSIGNED - see Data Note]£1,200–£2,800 [PLACEHOLDER - confirm vs cost sheet]Twin-cam six - reliable but cooling system requires attention

E46

1998–2000M52TUB20★★★★☆ [NEWLY ASSIGNED - see Data Note]£1,300–£3,000 [PLACEHOLDER - confirm vs cost sheet]Double VANOS six - 150 bhp

E46

2000–2005M54B22★★★★☆ [NEWLY ASSIGNED - see Data Note]£1,400–£3,200 [PLACEHOLDER - confirm vs cost sheet]2.2-litre six - 170 bhp. Valve cover gasket and cooling system weak points

E90

2005–2007N46B20★★★☆☆ [NEWLY ASSIGNED - see Data Note]£1,600–£3,500 [PLACEHOLDER - confirm vs cost sheet]Last of the naturally aspirated fours - 150 bhp. Timing chain issues

E90

2007–2011N43B20★★☆☆☆ [NEWLY ASSIGNED - see Data Note]£1,800–£4,000 [PLACEHOLDER - confirm vs cost sheet]Direct-injection four - timing chain and NOx sensor problems

F30

2012–2015N20B20★★★☆☆ [NEWLY ASSIGNED - see Data Note]£2,500–£5,000 [PLACEHOLDER - confirm vs cost sheet]First turbocharged 320i - 184 bhp. Timing chain guide failure risk

F30

2015–2019B48B20★★★★☆ [NEWLY ASSIGNED - see Data Note]£3,000–£6,000 [PLACEHOLDER - confirm vs cost sheet]Modular turbo four - significantly improved reliability

G20

2019–presentB48B20★★★★☆ [NEWLY ASSIGNED - see Data Note]£3,200–£7,500 [PLACEHOLDER - confirm vs cost sheet]Modern B48 - 184 bhp, 300 Nm. Coolant leaks and PCV wear

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 3 Series 320i Engine Replacement Costs

Supply Only£1,800–£6,000

Fitted (Indie)£2,800–£7,500

Warranty12–24 months

Best ForMost owners - best cost/warranty balance

Engine TypeSupply OnlyFitted (Indie)WarrantyBest For

Used Engine£900–£2,500£1,800–£3,8001–6 monthsBudget priority; older E21–E46 cars

Reconditioned Engine£1,800–£6,000£2,800–£7,50012–24 monthsMost owners - best cost/warranty balance

Rebuilt Engine£3,000–£7,500£4,000–£9,00012–24 monthsLong-term ownership; 3+ year horizon

Main Dealer New£6,000–£10,000£7,500–£12,00024–36 monthsInsurance jobs, warranty claims (modern cars only)

Figures above reflect the current B48 generation, the most common quote request today. Older generations: see the Era Map above for M10, M20, M50, M52, M54, N46, and N43-specific pricing, which runs significantly lower.

Labour estimate: Fitting a 3 Series 320i engine typically takes 8–14 hours at £65–£95/hr (independent). Four-cylinder engines are generally more accessible; six-cylinder E30–E46 cars require more time.

→ Compare 3 Series 320i engine prices from UK specialists

Common Problems With BMW 320d Engines

1. N43 Timing Chain Failure (E90 2007–2011)

Symptoms: Rattling noise from the engine on cold start, metallic ticking, engine warning light, loss of power. Chain guides can break up and block the oil pickup.

Typical mileage: 30,000–100,000 miles - failures have been reported from just 30,000 miles.

Repair cost: £800–£2,500 (chain, tensioner, guides).

Replacement cost: N/A - repair only if caught early; catastrophic failure requires full engine replacement.

🔴 Immediate - if you hear rattle, book an inspection today.

Our recommendation:

The N43 is widely considered one of the worst engines BMW ever made. The excessive 18,000-mile service interval is a major contributor to failure - chain guides break up and debris blocks the oil pickup. A preventative chain replacement is essential on any high-mileage N43. At the first sign of cold-start rattle - or even without, as some fail without warning - book an inspection immediately.

1. N43 Timing Chain Failure (E90 2007–2011)

Symptoms: Rattling noise from the engine on cold start, metallic ticking, engine warning light, loss of power. Chain guides can break up and block the oil pickup.

Typical mileage: 30,000–100,000 miles - failures have been reported from just 30,000 miles.

Repair cost: £800–£2,500 (chain, tensioner, guides).

Replacement cost: N/A - repair only if caught early; catastrophic failure requires full engine replacement.

🔴 Immediate - if you hear rattle, book an inspection today.

Our recommendation:

2. <a href='https://bmwengines.uk/engine/n13-n20'>N20</a> Timing Chain Guide Failure (F30 2012–2015)

Symptoms: Rattling noise on cold start, metallic ticking, engine warning light, loss of power.

Typical mileage: 40,000–80,000 miles - early production cars (pre-March 2015) are most at risk.

Repair cost: £1,200–£3,000 (chain, tensioner, guides).

Replacement cost: N/A - repair only if caught early; catastrophic failure requires full engine replacement.

🔴 Immediate - at first sign of rattle, book inspection today.

Our recommendation:

The N20's timing chain tensioner can fail, causing the chain to slip or break. If the tensioner fails completely, it can lead to catastrophic engine failure. Early production N20s (pre-March 2015) are most susceptible. Many specialists recommend preventative chain replacement at 60,000–80,000 miles regardless of symptoms.

3. Cooling System Failures (E36–E46 M50/M52/M54)

Symptoms: Coolant loss, overheating, steam from engine bay, low coolant warning.

Typical mileage: 60,000–120,000 miles - age-related as plastic components become brittle.

Repair cost: £200–£800 (expansion tank, water pump, thermostat).

Replacement cost: N/A - repair only; ignoring coolant warnings can lead to head gasket failure.

🔴 Immediate - if the coolant warning comes on, pull over and let the engine cool.

Our recommendation:

The cooling systems on E36 and E46 six-cylinder 320is are well-documented weak points. The plastic expansion tank, water pump impeller, and thermostat housing all degrade with age. If you see any coolant warnings, have the system inspected immediately - overheating can cause head gasket failure on these otherwise robust engines.

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3 Series 320i - 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.

3 Series 320i - 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 SenseN43 timing chain rattle✅ Yes (if caught early)£800–£2,500Preventative - catches fault before catastrophic failureN20 timing chain guide failure✅ Yes (if caught early)£1,200–£3,000Preventative - many specialists recommend at 60k milesCooling system failure (E36/E46)✅ Yes£200–£800Simple fix - do it immediately to avoid head gasket failureValve cover gasket leak (M54/N46)✅ Yes£200–£500Common maintenance item - repair when symptoms appearSnapped timing chain (N43/N20)❌ Usually NoEngine replacementInterference engine - piston-valve contact means little is left to repair

Buying This 320i? Check These First

Buy If

Pre-2005 six-cylinder (E21–E46) with full service history - robust and characterful
Post-2015 B48 (F30 LCI or G20) - significantly improved reliability over N20
N20 with documented timing chain replacement (especially if pre-March 2015)
Cooling system recently serviced on E36/E46 cars

Avoid If

2007–2011 N43 with cold-start rattle and no chain history - the worst 320i engine
Pre-March 2015 N20 without timing chain documentation
Overheating or coolant loss on any generation - can indicate head gasket failure
Poor service history on any generation - these engines are unforgiving of neglect

Closing Verdict

The 320i badge spans five decades and a huge range of engines - from the bulletproof M20 six to the problematic N43 four. The six-cylinder cars (E21–E46) are the most durable; the N43 is best avoided entirely; the N20 needs timing chain vigilance; and the B48 (2015+) is the modern sweet spot. With the 70% BMW scrap threshold, a £4,000 recon on a £6,000 320i is 67% - borderline. On a sub-£5,000 example, think carefully.

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

→ Compare 3 Series 320i engine prices before you buy

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Buying Checklist

Before you buy a used BMW 3 Series 320i (or before you commit to an engine replacement), check these:

Cold Start

Listen for rattling on startup (N43/N20 timing chain warning)

Service History

Including which engine era and confirmed oil-interval discipline

Coolant Check

Check level and condition - overheating kills these engines

Timing Chain Documentation

Any evidence of chain replacement on N43/N20?

Smoke Check

Blue smoke could indicate valve stem seals or piston rings

Oil Leaks

Check around valve cover (M54/N46 common) and oil filter housing

Engine Warning Light

Have codes been read? Any unresolved issues?

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 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.

M10B20

Years1975–1982

Power125 bhp (92 kW)

2025 Enquiries- (pattern data)

Avg. Recon Cost£900–£2,200 [PLACEHOLDER]

Engine CodeYearsPower2025 EnquiriesAvg. Recon Cost

M10B201975–1982125 bhp (92 kW)- (pattern data)£900–£2,200 [PLACEHOLDER]

M20B201982–1991125 bhp (92 kW)- (pattern data)£1,000–£2,500 [PLACEHOLDER]

M50B20 / M52B201991–1998150 bhp (110 kW)- (pattern data)£1,200–£2,800 [PLACEHOLDER]

M52TUB201998–2000150 bhp (110 kW)- (pattern data)£1,300–£3,000 [PLACEHOLDER]

M54B222000–2005170 bhp (125 kW)- (pattern data)£1,400–£3,200 [PLACEHOLDER]

N46B202005–2007150 bhp (110 kW)- (pattern data)£1,600–£3,500 [PLACEHOLDER]

N43B202007–2011170 bhp (125 kW)- (pattern data)£1,800–£4,000 [PLACEHOLDER]

N20B202012–2015184 bhp (135 kW)- (pattern data)£2,500–£5,000 [PLACEHOLDER]

B48B202015–present184 bhp (135 kW)- (pattern data)£3,000–£7,500 [PLACEHOLDER]

Technical Specs

current B48B20 generation

Displacement1,998 cc

Cylinders4-cylinder inline

Compression Ratio11.0:1

Fuel SystemDirect injection

TurbochargerTwinPower Turbo

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Market Intelligence

Most Common Failure

N43 timing chain

reported from as little as 30,000 miles 【PATTERN DATA】

Average Enquiry Mileage

75,000

miles 【PATTERN DATA】

Average Replacement Cost

£3,500 reconditioned, supply only 【PLACEHOLDER

confirm vs cost sheet】

Most Requested Engine Code

N20B20 (F30 320i

highest-volume modern variant) 【PATTERN DATA】

Peak Enquiry Season

Winter

cold starts expose timing chain issues 【PATTERN DATA】

Regional Demand

London20%

South East18%

North West (14%) 【PATTERN DATA】

Regional Demand Breakdown

20%London

18%South East

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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supply-only or full supply & fit available nationwide, covering everything from cooling system repair to timing chain replacement to full engine swaps.

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