How much does a BMW M340i engine replacement cost in the UK?

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.

What are the common problems with the BMW M340i?

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.

Is it worth replacing a BMW M340i engine, or should I scrap the car?

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.

How do I find my BMW M340i engine code?

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.

Does the B58 have a cambelt or timing chain?

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.

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

BMW M340i Engine Replacement — Compare Prices & Get Quotes

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

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

Instant QuotesNo Obligation100% FreeReconditionedRebuiltUsedSupply & Fit AvailableUK-Wide Network

BMW M340i - Which Engine Does Your Car Actually Have?

Four generations. Four 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

GenerationYearsEngine CodeReliabilityRecon CostEra Note

G20/G21 (pre-LCI) BMW 320d G20/G21 (pre-LCI)

2019–2022B58B30O1 (B58TU1)★★★★☆ [NEWLY ASSIGNED - see Data Note]£4,000–£6,500 [PLACEHOLDER]3.0L turbo inline-six - 374 PS, 500 Nm. One-piece timing chain, upgraded cooling system

G20/G21 (LCI) BMW 320d G20/G21 (LCI)

2022–presentB58B30O1 (B58TU2)★★★★☆ [NEWLY ASSIGNED - see Data Note]£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 UK Cost Data

Verified Reliability

Expert Insights

Updated for 2025

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 TypeSupply OnlyFitted (Indie)WarrantyBest For

Used Engine£2,000–£4,500£3,000–£6,0001–6 monthsBudget priority; lower-mileage donor

Reconditioned Engine£4,000–£6,500£6,000–£8,50012–24 monthsMost owners - best cost/warranty balance

Rebuilt Engine£5,000–£8,500£7,000–£10,00012–24 monthsLong-term ownership; 3+ year horizon

Main Dealer New£14,000–£18,000+£16,000–£20,000+24–36 monthsInsurance 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).

→ Compare M340i engine prices from UK specialists

Common Problems With BMW 320d 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)

🟠 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]

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)

🟠 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]

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

🟡 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]

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

🟡 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

Weighing Your Options?

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M340i - 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.

M340i - 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 SenseCoolant system plastic connector✅ Yes£300–£800Upgraded aluminium connector is a permanent fixOil filter housing leak✅ Yes£400–£800Catch early to prevent coolant-oil contaminationValve cover gasket leak✅ Yes£400–£1,200Viable on any well-maintained exampleVANOS solenoid failure✅ Yes£300–£600Straightforward component replacementCrank hub failure (rare)⚠️ Sometimes£3,000–£6,000Rare 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.

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

→ Compare M340i engine prices before you buy

Don't Guess. Compare.

Get real quotes from vetted UK specialists and make the right call for your 320d.

→ Compare M340i engine prices before you buy

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Buying Checklist

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

Coolant Level

Check for frequent top-ups; inspect for leaks around the heat management module

Oil Leaks

Look for oil residue around the valve cover and oil filter housing

Cold Start

Listen for any unusual rattling or ticking (B58 timing chain is generally robust)

Service History

Including the B58 engine and confirmed BMW-approved oil changes

VANOS Health

Any power loss, rough idle, or hesitation? Check for fault codes

Engine Warning Light

Have codes been read? Look for VANOS or cooling system codes

Brake & Transmission

Check for smooth gear changes; ZF 8HP is robust but benefits from fluid changes

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.

B58B30O1 (B58TU1)

Years2019–2022

Power374 PS (275 kW) / 500 Nm

2025 Enquiries- (pattern data)

Avg. Recon Cost£4,000–£6,500【PLACEHOLDER】

Engine CodeYearsPower2025 EnquiriesAvg. Recon Cost

B58B30O1 (B58TU1)2019–2022374 PS (275 kW) / 500 Nm- (pattern data)£4,000–£6,500【PLACEHOLDER】

B58B30O1 (B58TU2)2022–present374 PS (275 kW) / 500 Nm- (pattern data)£4,000–£6,500【PLACEHOLDER】

Technical Specs

B58B30O1

Displacement2,998 cc (3.0L)

Cylinders6-cylinder inline

Bore82 mm / Stroke: 94.6 mm

Cylinder BlockClosed-deck aluminium

Cylinder HeadAluminium

ValvetrainDOHC, 4 valves per cylinder, Valvetronic, Double VANOS

Valvetrain DriveChain

Compression Ratio11.0:1

Fuel SystemDirect injection

TurbochargerSingle twin-scroll turbo with air-to-liquid intercooler

Power374 PS (275 kW)

Torque500 Nm

0-60 mph4.2–4.4 seconds

→ Compare M340i engine prices for your BMW

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Market Intelligence

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

London22%

South East18%

North West (12%)【PATTERN DATA】

Regional Demand Breakdown

22%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.

Why UK BMW M340i Owners Trust BMWEngines.uk

Trusted M340i Engine Suppliers
every garage and engine rebuilder in our network is vetted, rated and reviewed by real M340i owners, across both B58TU1 and B58TU2 variants, as part of the Engine Finders network.
Compare M340i Engine Replacement Companies
see prices, warranty terms and supply & fit options side-by-side before you commit.
UK Engine Replacement Services for M340i
supply-only or full supply & fit available nationwide, covering every G20/G21 M340i since 2019.

Find the best BMW M340i engine replacement UK drivers rely on. Compare prices from trusted specialists on EnginesMarket today and get back on the road with confidence.

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No hidden fees

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Get quotes with zero pressure

UK Specialists

20+ vetted experts

12-Month Warranty

As standard

Nationwide Delivery

Supply & fit available