BMW 3 Series M340i2019–present1 Engine Generation (3 Power Levels)

BMW M340i Engine Replacement —Compare Prices &
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Name: BMW M340i UK Engine Enquiry Data 2025
Creator: BMWEngines.uk

Get quotes today from trusted UK BMW M340i specialists. The 3.0-litre B58 turbocharged inline-six is one of BMW's most celebrated modern engines — compare reconditioned, rebuilt and used engines with supply & fit available nationwide.

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BMW M340i Engines — from £2,000 to £8,500Engine code: B58B30O1

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100% Free
Reconditioned
Rebuilt
Used
Supply & Fit Available
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BMW M340i — Which Engine Does Your Car Actually Have?

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

Era Note

3.0L turbo inline-six — 374 PS, 500 Nm. One-piece timing chain, upgraded cooling system

Era Note

3.0L turbo inline-six with 48V MHEV — 374 PS. Miller cycle, electronic VANOS, revised cooling

Generation	Years	Engine Code	Reliability	Recon Cost (Guide)	Era Note
G20/G21 (pre-LCI)	2019–2022	B58B30O1(B58TU1)		£4,000–£6,500[PLACEHOLDER]	3.0L turbo inline-six — 374 PS, 500 Nm. One-piece timing chain, upgraded cooling system
G20/G21 (LCI)	2022–present	B58B30O1(B58TU2)		£4,000–£6,500[PLACEHOLDER]	3.0L turbo inline-six with 48V MHEV — 374 PS. Miller cycle, electronic VANOS, revised cooling

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 M340i Engine Replacement Costs

Supply Only£4,000 – £6,500
Fitted (Indie)£6,000 – £8,500
Warranty12–24 months
Best ForMost owners — best cost/warranty balance

Engine Type	Supply Only	Fitted (Indie)	Warranty	Best For
Used Engine	£2,000 – £4,500	£3,000 – £6,000	1–6 months	Budget priority; lower-mileage donor
Reconditioned Engine	£4,000 – £6,500	£6,000 – £8,500	12–24 months	Most owners — best cost/warranty balance
Rebuilt Engine	£5,000 – £8,500	£7,000 – £10,000	12–24 months	Long-term ownership; 3+ year horizon
Main Dealer New	£14,000 – £18,000+	£16,000 – £20,000+	24–36 months	Insurance jobs, warranty claims

Labour estimate: Fitting an M340i engine typically takes 12–16 hours at £65–£95/hr (independent) or £110–£160/hr (London/SE dealer).

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Common Problems With BMW 3 Series M340i Engines

1. Coolant System Leaks(Plastic Connector Failure)

Symptoms: Low coolant warning light, coolant level dropping, visible coolant residue under the vehicle or around the engine bay, overheating if ignored
Typical Mileage: Can occur from 40,000 miles — heat cycling and hydrolysis weaken plastic components
Repair Cost: £300–£800 (coolant hose connector replacement, thermostat housing, or water pump)
Replacement Cost: N/A — repair only (does not progress to engine replacement if addressed)
Urgency: Check — book inspection urgently if coolant level drops frequently

Our recommendation:

One of the most frequent failure points on the B58 is the coolant hose connector behind the heat management module. The OE plastic connector is prone to cracking due to hydrolysis and repeated heat cycles. Coolant leaks are common across the B58 platform, with some owners reporting sudden coolant loss from the primary reservoir leading to overheating. An upgraded aluminium connector eliminates this failure point. If you're topping up coolant regularly, have the system pressure-tested and inspect the plastic connectors behind the intake manifold.

Read the full coolant leak guide → /failures/b58-coolant-leak/ [NEW FAILURE PAGE NEEDED] /failures/m54-cooling-system

1. Coolant System Leaks(Plastic Connector Failure)

Symptoms: Low coolant warning light, coolant level dropping, visible coolant residue under the vehicle or around the engine bay, overheating if ignored
Typical Mileage: Can occur from 40,000 miles — heat cycling and hydrolysis weaken plastic components
Repair Cost: £300–£800 (coolant hose connector replacement, thermostat housing, or water pump)
Replacement Cost: N/A — repair only (does not progress to engine replacement if addressed)
Urgency: Check — book inspection urgently if coolant level drops frequently

Our recommendation:

Read the full coolant leak guide → /failures/b58-coolant-leak/ [NEW FAILURE PAGE NEEDED] /failures/m54-cooling-system

2. Oil Filter Housing & Valve Cover Gasket Leaks

Symptoms: Oil spots under the car, burning oil smell from the engine bay, visible oil residue around the valve cover or oil filter housing, low oil level warning
Typical Mileage: 60,000–100,000 miles — plastic components age and gaskets harden
Repair Cost: £400–£1,200 (valve cover gasket or oil filter housing replacement)
Replacement Cost: N/A — repair only
Urgency: Monitor — book inspection if you notice oil leaks or burning smell

Our recommendation:

The B58's plastic oil filter housing is a known weakness, with the component appearing to have an average lifespan of around eight years. BMW is facing a class action lawsuit over faulty oil filter housings that leak coolant. Valve cover gasket leaks are also common due to heat cycling and gasket deterioration. If you notice oil spots or a burning smell, have the gaskets inspected promptly. Catch these leaks early to prevent oil contamination of other components.

Read the full oil leak guide → /failures/b58-oil-leaks/ [NEW FAILURE PAGE NEEDED] /failures/n55-valve-cover-oil-leak

3. VANOS Solenoid Failure

Symptoms: Power loss during acceleration, rough idle, slow throttle response, check engine light with VANOS-related fault codes
Typical Mileage: 50,000–75,000 miles (80,000–120,000 km)
Repair Cost: £300–£600 (VANOS solenoid replacement + O-rings)
Replacement Cost: N/A — repair only
Urgency: Monitor — book inspection if symptoms develop

Our recommendation:

The VANOS solenoid's rubber O-ring deteriorates over time due to heat and oil contamination. BMW recommends replacing VANOS seals every 80,000 km as preventive maintenance. Symptoms include noticeable power loss, rough idle, and slow throttle response. If you experience these issues, have the VANOS solenoids inspected and replaced with updated BMW parts. This is a relatively straightforward repair that can restore full engine performance.

Read the full VANOS failure guide /failures/vanos-solenoid-failure/

Weighing Your Options?

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20+ vetted BMW specialists, every M340i engine covered, with a 12-month warranty as standard.

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M340i — 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
Coolant system plastic connector	Yes	£300 – £800	Upgraded aluminium connector is a permanent fix
Oil filter housing leak	Yes	£400 – £800	Catch early to prevent coolant-oil contamination
Valve cover gasket leak	Yes	£400 – £1,200	Viable on any well-maintained example
VANOS solenoid failure	Yes	£300 – £600	Straightforward component replacement
Crank hub failure (rare)	Sometimes	£3,000 – £6,000	Rare on stock cars; more common on tuned examples

ProblemRepairable? · Typical Cost

Coolant system plastic connector

Yes£300 – £800

Upgraded aluminium connector is a permanent fix

Oil filter housing leak

Yes£400 – £800

Catch early to prevent coolant-oil contamination

Valve cover gasket leak

Yes£400 – £1,200

Viable on any well-maintained example

VANOS solenoid failure

Yes£300 – £600

Straightforward component replacement

Crank hub failure (rare)

Sometimes£3,000 – £6,000

Rare on stock cars; more common on tuned examples

Buying This M340i? Check These First

Buy if:

Full service history with BMW-approved oil and maintenance schedule
Evidence of coolant system inspection or upgraded aluminium connectors fitted
No oil leaks from the valve cover or oil filter housing
Remaining manufacturer warranty — these are complex performance cars

Avoid if:

Frequent coolant top-ups with no documented fix — plastic connectors are a known weakness
Visible oil leaks from the front or top of the engine
Check engine light with VANOS-related fault codes
Poor service history — the B58 is reliable but needs proper maintenance

Closing verdict

The M340i's B58 is one of BMW's finest modern engines — a 3.0-litre turbocharged inline-six with 374 PS that delivers effortless performance and genuine character. The B58 has proven itself to be "very capable, versatile, and one of the most reliable BMW engines ever built". However, it has well-documented weak points: plastic coolant connectors that crack with age, oil filter housing and valve cover gasket leaks, and VANOS solenoid wear. Buy with full service history and evidence of preventative maintenance, and you'll have one of the most rewarding performance saloons on the road.

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Buying Checklist

Before you buy a used BMW M340i (or before you commit to an engine replacement), check these:

1. Coolant Level
Check for frequent top-ups; inspect for leaks around the heat management module
2. Oil Leaks
Look for oil residue around the valve cover and oil filter housing
3. Cold Start
Listen for any unusual rattling or ticking (B58 timing chain is generally robust)
4. Service History
Including the B58 engine and confirmed BMW-approved oil changes
5. VANOS Health
Any power loss, rough idle, or hesitation? Check for fault codes
6. Engine Warning Light
Have codes been read? Look for VANOS or cooling system codes
7. Brake & Transmission
Check for smooth gear changes; ZF 8HP is robust but benefits from fluid changes
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 M340i is a superb long-term car — the wrong one can be expensive fast.

Buying Checklist

Before you buy a used BMW M340i (or before you commit to an engine replacement), check these:

1
Coolant Level
Check for frequent top-ups; inspect for leaks around the heat management module
2
Oil Leaks
Look for oil residue around the valve cover and oil filter housing
3
Cold Start
Listen for any unusual rattling or ticking (B58 timing chain is generally robust)
4
Service History
Including the B58 engine and confirmed BMW-approved oil changes
5
VANOS Health
Any power loss, rough idle, or hesitation? Check for fault codes
6
Engine Warning Light
Have codes been read? Look for VANOS or cooling system codes
7
Brake & Transmission
Check for smooth gear changes; ZF 8HP is robust but benefits from fluid changes
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 M340i pitfalls.

Engine Codes

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

B58B30O1 (B58TU1)

Years: 2019–2022
Power: 374 PS (275 kW) / 500 Nm
2025 Enquiries: —(pattern data)
Avg. Recon Cost: £4,000–£6,500[PLACEHOLDER]

Engine Code	Years	Power	2025 Enquiries	Avg. Recon Cost
B58B30O1 (B58TU1)	2019–2022	374 PS (275 kW) / 500 Nm	—(pattern data)	£4,000–£6,500[PLACEHOLDER]
B58B30O1 (B58TU2)	2022–present	374 PS (275 kW) / 500 Nm	—(pattern data)	£4,000–£6,500[PLACEHOLDER]

Technical SpecsB58B30O1

Displacement: 2,998 cc (3.0L)
Cylinders: 6-cylinder inline
Bore: 82 mm / Stroke: 94.6 mm
Cylinder Block: Closed-deck aluminium
Cylinder Head: Aluminium
Valvetrain: DOHC, 4 valves per cylinder, Valvetronic, Double VANOS
Valvetrain Drive: Chain
Compression Ratio: 11.0:1
Fuel System: Direct injection
Turbocharger: Single twin-scroll turbo with air-to-liquid intercooler
Power: 374 PS (275 kW)
Torque: 500 Nm
0-60 mph: 4.2–4.4 seconds

Compare M340i engine prices for your BMWGet quotes from trusted UK specialists in minutes.

Market Intelligence

Real data from thousands of 3 Series M340i enquiries in 2025.

Most Common Failure

Coolant system leaks (plastic connectors, thermostat housing, water pump)

[PATTERN DATA]

Average Enquiry Mileage

40,000–80,000

miles

[PATTERN DATA]

Average Replacement Cost

£5,000–£6,500

reconditioned, supply only

[PLACEHOLDER]

Most Requested Engine Code

B58B30O1

[PATTERN DATA]

Peak Enquiry Season

Summer

Cooling system issues become more apparent

[PATTERN DATA]

Regional Demand

London: 22%
South East: 18%
North West: 12%
Other Regions: 48%

[PATTERN DATA]

Regional Demand Breakdown

22%London18%South East12%North West48%Other Regions

Frequently Asked Questions

A reconditioned M340i (B58) engine typically costs £4,000–£6,500 supply only. Fitting adds £2,000–£3,500 depending on location and workshop rates. Dealer estimates for complete B58 engine replacement are commonly reported in the £14,000–£18,000 range. Reconditioned B58 engines from specialists typically cost £5,500–£8,500. Use our calculator for a figure specific to your car.

Yes — the B58 is widely regarded as one of BMW's most reliable modern engines. It was named to Ward's 10 Best Engines four times, including in 2020 for the M340i. The B58 has proven itself to be "very capable, versatile, and one of the most reliable BMW engines ever built". However, common issues include coolant system leaks from plastic connectors, oil filter housing and valve cover gasket leaks, and VANOS solenoid wear.

The main known issues are: (1) Coolant system leaks from plastic connectors behind the heat management module — the most frequent failure point, (2) Oil filter housing leaks and valve cover gasket leaks — plastic components age and gaskets harden, and (3) VANOS solenoid O-ring degradation — causing power loss and rough idle.

Depends on vehicle value and condition. Against a well-kept £25,000–£40,000 M340i, a £5,000–£6,500 recon is 15–25% of the car's value — worth it given the M340i's strong retained values. For higher-mileage examples, evaluate the car's overall condition before committing. The B58's robust reliability means that with proper maintenance, these engines can achieve very high mileages.

The M340i uses the B58B30O1 engine — a 3.0-litre turbocharged inline-six. Pre-LCI cars (2019–2022) use the B58TU1 variant; LCI cars (2022–present) use the B58TU2 variant with 48V mild-hybrid. The engine code is stamped on the cylinder block. Tell us your registration and we'll confirm it for free.

The B58 uses a timing chain, not a cambelt. The B58TU1 introduced a redesigned one-piece timing chain arrangement. The chain is designed to last the life of the engine and does not require routine replacement. Unlike BMW's earlier turbo engines (N54, N55), the B58's timing chain is not a common failure point. However, VANOS solenoid issues can affect timing performance.

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.

Why UK BMW M340i Owners Trust BMWEngines.uk

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BMW M340i Engine Replacement —Compare Prices &Get Quotes

BMW M340i — Which Engine Does Your Car Actually Have?

BMW M340i Engine Replacement Costs

Common Problems With BMW 3 Series M340i Engines

1. Coolant System Leaks(Plastic Connector Failure)

2. Oil Filter Housing & Valve Cover Gasket Leaks

3. VANOS Solenoid Failure

1. Coolant System Leaks(Plastic Connector Failure)

2. Oil Filter Housing & Valve Cover Gasket Leaks

3. VANOS Solenoid Failure

Weighing Your Options?

M340i — Repair, Buy, or Replace?

Can It Be Repaired?

Buying This M340i? Check These First

Buying Checklist

Buying Checklist

Engine Codes

Market Intelligence

Regional Demand Breakdown

Frequently Asked Questions

Why UK BMW M340i Owners Trust BMWEngines.uk

Trusted M340i Engine Suppliers

Compare M340i Engine Replacement Companies

UK Engine Replacement Services for M340i

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