BMW 3 Series 320i1975–present9 Engine Generations

BMW 3 Series 320i Engine Replacement —Compare Prices &
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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

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The 320i Through Time — Era Map

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

Era Note

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

Era Note

Silky-smooth six-cylinder — one of BMW's most durable engines

Era Note

Twin-cam six — reliable but cooling system requires attention

Era Note

Double VANOS six — 150 bhp

Era Note

2.2-litre six — 170 bhp. Valve cover gasket and cooling system weak points

Era Note

Last of the naturally aspirated fours — 150 bhp. Timing chain issues

Era Note

Direct-injection four — timing chain and NOx sensor problems

Era Note

First turbocharged 320i — 184 bhp. Timing chain guide failure risk

Era Note

Modular turbo four — significantly improved reliability

Era Note

Modern B48 — 184 bhp, 300 Nm. Coolant leaks and PCV wear

Generation	Years	Engine Code	Recon Cost (Guide)	Era Note
E21	1975–1982	M10B20	£900–£2,200[PLACEHOLDER]	Original fuel-injected 320i — robust but now rare and ageing
E30	1982–1991	M20B20	£1,000–£2,500[PLACEHOLDER]	Silky-smooth six-cylinder — one of BMW's most durable engines
E36	1991–1998	M50B20 / M52B20	£1,200–£2,800[PLACEHOLDER]	Twin-cam six — reliable but cooling system requires attention
E46	1998–2000	M52TUB20	£1,300–£3,000[PLACEHOLDER]	Double VANOS six — 150 bhp
E46	2000–2005	M54B22	£1,400–£3,200[PLACEHOLDER]	2.2-litre six — 170 bhp. Valve cover gasket and cooling system weak points
E90	2005–2007	N46B20	£1,600–£3,500[PLACEHOLDER]	Last of the naturally aspirated fours — 150 bhp. Timing chain issues
E90	2007–2011	N43B20	£1,800–£4,000[PLACEHOLDER]	Direct-injection four — timing chain and NOx sensor problems
F30	2012–2015	N20B20	£2,500–£5,000[PLACEHOLDER]	First turbocharged 320i — 184 bhp. Timing chain guide failure risk
F30	2015–2019	B48B20	£3,000–£6,000[PLACEHOLDER]	Modular turbo four — significantly improved reliability
G20	2019–present	B48B20	£3,200–£7,500[PLACEHOLDER]	Modern B48 — 184 bhp, 300 Nm. Coolant leaks and PCV wear

Why use this era map?

Every cost guide, reliability rating and engine code on this page is aligned to the data above. This keeps everything consistent and trustworthy.

Real UKCost Data
VerifiedReliability
ExpertInsights
Updated for2025

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 Type	Supply Only	Fitted (Indie)	Warranty	Best For
Used Engine	£900 – £2,500	£1,800 – £3,800	1–6 months	Budget priority; older E21–E46 cars
Reconditioned Engine	£1,800 – £6,000	£2,800 – £7,500	12–24 months	Most owners — best cost/warranty balance
Rebuilt Engine	£3,000 – £7,500	£4,000 – £9,000	12–24 months	Long-term ownership; 3+ year horizon
Main Dealer New	£6,000 – £10,000	£7,500 – £12,000	24–36 months	Insurance 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.

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Common Problems With BMW 3 Series 320i 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.
Urgency: 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.
Urgency: Immediate — if you hear rattle, book an inspection today.

Our recommendation:

2. N20 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.
Urgency: 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.
Urgency: 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?

Not every issue means a new engine.Here’s what can be repaired, when it makes sense, and what to check before you buy.

Can It Be Repaired?

Problem	Repairable?	Typical Cost	When It Makes Sense
N43 timing chain rattle	Yes (if caught early)	£800 – £2,500	Preventative — catches fault before catastrophic failure
N20 timing chain guide failure	Yes (if caught early)	£1,200 – £3,000	Preventative — many specialists recommend at 60k miles
Cooling system failure (E36/E46)	Yes	£200 – £800	Simple fix — do it immediately to avoid head gasket failure
Valve cover gasket leak (M54/N46)	Yes	£200 – £500	Common maintenance item — repair when symptoms appear
Snapped timing chain (N43/N20)	Usually No	Engine replacement	Interference engine — piston-valve contact means little is left to repair

ProblemRepairable? · Typical Cost

N43 timing chain rattle

Yes (if caught early)£800 – £2,500

Preventative — catches fault before catastrophic failure

N20 timing chain guide failure

Yes (if caught early)£1,200 – £3,000

Preventative — many specialists recommend at 60k miles

Cooling system failure (E36/E46)

Yes£200 – £800

Simple fix — do it immediately to avoid head gasket failure

Valve cover gasket leak (M54/N46)

Yes£200 – £500

Common maintenance item — repair when symptoms appear

Snapped timing chain (N43/N20)

Usually NoEngine replacement

Interference 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.

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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:

1. Cold Start
Listen for rattling on startup (N43/N20 timing chain warning)
2. Service History
Including which engine era and confirmed oil-interval discipline
3. Coolant Check
Check level and condition — overheating kills these engines
4. Timing Chain Documentation
Any evidence of chain replacement on N43/N20?
5. Smoke Check
Blue smoke could indicate valve stem seals or piston rings
6. Oil Leaks
Check around valve cover (M54/N46 common) and oil filter housing
7. Engine Warning Light
Have codes been read? Any unresolved issues?
8. MOT History
Check for emissions-related failures

Why this matters

A 10-minute check now can save you thousands later. The right 3 Series 320i is a superb long-term car — the wrong one can be expensive fast.

Buying Checklist

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

1
Cold Start
Listen for rattling on startup (N43/N20 timing chain warning)
2
Service History
Including which engine era and confirmed oil-interval discipline
3
Coolant Check
Check level and condition — overheating kills these engines
4
Timing Chain Documentation
Any evidence of chain replacement on N43/N20?
5
Smoke Check
Blue smoke could indicate valve stem seals or piston rings
6
Oil Leaks
Check around valve cover (M54/N46 common) and oil filter housing
7
Engine Warning Light
Have codes been read? Any unresolved issues?
8
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 3 Series 320i pitfalls.

Engine Codes

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

M10B20

Years: 1975–1982
Power: 125 bhp (92 kW)
2025 Enquiries: —(pattern data)
Avg. Recon Cost: £900–£2,200[PLACEHOLDER]

Engine Code	Years	Power	2025 Enquiries	Avg. Recon Cost
M10B20	1975–1982	125 bhp (92 kW)	—(pattern data)	£900–£2,200[PLACEHOLDER]
M20B20	1982–1991	125 bhp (92 kW)	—(pattern data)	£1,000–£2,500[PLACEHOLDER]
M50B20 / M52B20	1991–1998	150 bhp (110 kW)	—(pattern data)	£1,200–£2,800[PLACEHOLDER]
M52TUB20	1998–2000	150 bhp (110 kW)	—(pattern data)	£1,300–£3,000[PLACEHOLDER]
M54B22	2000–2005	170 bhp (125 kW)	—(pattern data)	£1,400–£3,200[PLACEHOLDER]
N46B20	2005–2007	150 bhp (110 kW)	—(pattern data)	£1,600–£3,500[PLACEHOLDER]
N43B20	2007–2011	170 bhp (125 kW)	—(pattern data)	£1,800–£4,000[PLACEHOLDER]
N20B20	2012–2015	184 bhp (135 kW)	—(pattern data)	£2,500–£5,000[PLACEHOLDER]
B48B20	2015–present	184 bhp (135 kW)	—(pattern data)	£3,000–£7,500[PLACEHOLDER]

Technical Specscurrent B48B20 generation

Displacement: 1,998 cc
Cylinders: 4-cylinder inline
Compression Ratio: 11.0:1
Fuel System: Direct injection
Turbocharger: TwinPower Turbo

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Market Intelligence

Real data from thousands of 3 Series 320i enquiries in 2025.

Most Common FailureN43 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]

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

London: 20%
South East: 18%
North West: 14%
Other Regions: 48%

[PATTERN DATA]

Regional Demand Breakdown

20%London18%South East14%North West48%Other Regions

Frequently Asked Questions

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.

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.

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.

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.

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.

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.

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

The 320i Through Time — Era Map

BMW 3 Series 320i Engine Replacement Costs

Common Problems With BMW 3 Series 320i Engines

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

2. N20 Timing Chain Guide Failure(F30 2012–2015)

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

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

2. N20 Timing Chain Guide Failure(F30 2012–2015)

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

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3 Series 320i — Repair, Buy, or Replace?

Can It Be Repaired?

Buying This 320i? Check These First

Buying Checklist

Buying Checklist

Engine Codes

Market Intelligence

Regional Demand Breakdown

Frequently Asked Questions

Why UK BMW 3 Series 320i Owners Trust BMWEngines.uk

Trusted 3 Series 320i Engine Suppliers

Compare 3 Series 320i Engine Replacement Companies

UK Engine Replacement Services for 320i

BMW 3 Series 320i Engine Replacement —Compare Prices &
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