How much does a BMW M135i engine replacement cost in the UK?

A reconditioned M135i engine costs £3,800–£7,500 supply only depending on generation. F20 N55 engines start around £4,500, while F40 B48 units start around £3,800. Fitting adds £1,200–£1,800. Use our calculator for a figure specific to your car.

Is the BMW M135i engine reliable?

It depends entirely on which generation you have. The F20/F21 N55 is a proven straight-six - reliable but with known weak points (HPFP, chargepipe, VANOS solenoids). The F40 B48 is more modern and generally more reliable, but the car itself is a very different proposition - front-/all-wheel-drive and four-cylinder.

What are the common problems with the BMW M135i?

F20/F21 N55: HPFP failure, chargepipe failure (plastic cracks), VANOS solenoid wear. F40 B48: less common issues, but cooling system problems and occasional timing chain vigilance are noted.

Is it worth replacing a BMW M135i engine, or should I scrap the car?

Depends on vehicle value and which generation. Against a well-kept £18,000 F20, a £6,000 recon is 33% - worth it. Against a tired £8,000 F20 with other issues, the same recon exceeds our 70% BMW threshold. F40 values are higher - a £6,000 recon against a £30,000 car is 20% - definitely worth it.

How do I find my BMW M135i engine code?

Listed on the VIN plate and vehicle documentation. F20/F21 (2012-2019): N55B30A. F40 (2019-present): B48A20O1. The chassis code is the easiest tell: F20/F21 is the rear-drive hatch, F40 is the front-drive hatch.

Can I repair the HPFP on the N55, or does it need full engine replacement?

Yes - HPFP replacement is a well-understood repair costing £600–£1,200. It's the N55's most common weak point. If you experience long cranking or hesitation, don't ignore it - but it's a straightforward fix, not an engine killer.

BMW M135i2012–present2 Engine Generations

BMW M135i Engine Replacement — Compare Prices & Get Quotes

Name: BMW M135i UK Engine Enquiry Data 2025
Creator: BMWEngines.uk

Get quotes today from trusted UK BMW M Performance specialists. Compare reconditioned, rebuilt and used N55 and B48 engines - the straight-six and four-cylinder M135i eras - supply & fit available nationwide.

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BMW M135i Engines - from £2,500 to £10,500Common codes: N55B30A, B48A20O1

BMW M135i Engines - from £2,500 to £10,500· Common codes: N55B30A, B48A20O1

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The M135i THROUGH TIME - Era Map

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

Era Note

The original rear-wheel-drive M135i - a BMW purist's favourite. HPFP and chargepipe the weak points.

GenerationYearsEngine CodeReliabilityRecon CostEra Note

F20/F21

2012–2019N55B30A (3.0L Straight-Six Turbo)★★★☆☆ [NEWLY ASSIGNED - see Data Note]£4,500–£7,500 [PLACEHOLDER - confirm vs cost sheet]The original rear-wheel-drive M135i - a BMW purist's favourite. HPFP and chargepipe the weak points.

F40

2019–presentB48A20O1 (2.0L Four-Cylinder Turbo xDrive)★★★★☆ [NEWLY ASSIGNED - see Data Note]£3,800–£6,500 [PLACEHOLDER]The front-/all-wheel-drive generation - a genuinely different car under the same badge. More reliable, less character.

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 M135i Engine Replacement Costs

Supply Only£3,800–£7,500

Fitted (Indie)£5,000–£9,000

Warranty12–24 months

Best ForMost owners - best cost/warranty balance

Engine TypeSupply OnlyFitted (Indie)WarrantyBest For

Used Engine£2,500–£4,500£3,500–£5,8001–6 monthsBudget priority; older F20 examples

Reconditioned Engine£3,800–£7,500£5,000–£9,00012–24 monthsMost owners - best cost/warranty balance

Rebuilt Engine£5,500–£9,500£6,800–£11,00012–24 monthsLong-term ownership; 3+ year horizon

Main Dealer New£8,500–£14,000£10,000–£16,00024–36 monthsInsurance jobs, warranty claims

Figures above reflect the current B48 generation (F40), which has lower parts availability. Older F20 N55 engines typically run lower, with used examples starting around £2,500. See the Era Map above for generation-specific pricing.

Labour estimate: Fitting an M135i engine typically takes 12–16 hours at £70–£100/hr (independent) or £120–£180/hr (London/SE dealer).

→ Compare M135i engine prices from UK specialists

Common Problems With BMW 320d Engines

1. High-Pressure Fuel Pump (HPFP) Failure - N55 (F20/F21)

Symptoms: Long cranking on startup, hesitation under acceleration, engine stalling, engine warning light, reduced power.

Typical mileage: 40,000–80,000 miles.

Repair cost: £600–£1,200 (HPFP replacement) [PLACEHOLDER - confirm vs cost sheet]

Replacement cost: N/A - repair only

🟠 Check - book inspection urgently

Our recommendation:

The N55's HPFP is its most notorious weak point. If you experience long cranking or hesitation, don't ignore it - a failing HPFP can lead to lean running and catalytic converter damage. The replacement is well-understood and well-documented. This applies exclusively to the F20/F21 M135i.

Read the full HPFP failure guide

1. High-Pressure Fuel Pump (HPFP) Failure - N55 (F20/F21)

Symptoms: Long cranking on startup, hesitation under acceleration, engine stalling, engine warning light, reduced power.

Typical mileage: 40,000–80,000 miles.

Repair cost: £600–£1,200 (HPFP replacement) [PLACEHOLDER - confirm vs cost sheet]

Replacement cost: N/A - repair only

🟠 Check - book inspection urgently

Our recommendation:

Read the full HPFP failure guide

2. Chargepipe Failure - N55 (F20/F21)

Symptoms: Loss of boost, whistling noise from the engine bay, engine warning light, reduced power.

Typical mileage: 50,000–100,000 miles.

Repair cost: £300–£600 (chargepipe replacement with aftermarket metal unit)

Replacement cost: N/A - repair only

🟡 Monitor - book inspection soon

Our recommendation:

The N55's plastic chargepipe is prone to cracking, especially on tuned cars. The solution is an aftermarket metal chargepipe - fit once and forget. This is exclusively an F20/F21 issue; the F40 B48 uses a revised design.

Read the full chargepipe failure guide

3. VANOS Solenoid Wear - N55 (F20/F21)

Symptoms: Rough idle, reduced power at low RPM, hesitation, engine warning light with VANOS codes.

Typical mileage: 60,000–120,000 miles.

Repair cost: £200–£500 (VANOS solenoid replacement or cleaning)

Replacement cost: N/A - repair only

🟡 Monitor - book inspection soon

Our recommendation:

VANOS solenoid wear is common on higher-mileage N55 engines. The fix is relatively simple - cleaning or replacing the solenoids - but ignoring it can lead to timing issues. Regular oil changes with BMW LL-01 approved oil reduce the risk.

Read the full VANOS failure guide

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M135i - 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.

M135i - 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 SenseHPFP failure (N55)✅ Yes£600–£1,200Well-understood fix; cheaper than engine replacementChargepipe failure (N55)✅ Yes£300–£600Aftermarket metal unit solves permanentlyVANOS solenoid wear (N55)✅ Yes£200–£500Simple repair; part of routine maintenance on higher-mileage examplesHPFP failure (B48)✅ Yes£500–£1,000Less common than N55 but still possibleSnapped timing chain❌ Usually No£3,800–£9,500Typically requires full engine replacement

Buying This M135i? Check These First

Buy If

F20/F21: Documented HPFP and chargepipe replacement history (aftermarket metal chargepipe preferred)
F20/F21: Full service history with BMW LL-01 approved oil
F40: Full service history and no evidence of cooling system issues
Both: No cold-start rattle, misfires, or hesitation

Avoid If

F20/F21: No proof of HPFP or chargepipe maintenance - these are whens, not ifs
F20/F21: Poor service history - the N55 is unforgiving of neglect
F40: Cooling system issues with no documented repair
Both: Engine warning light with no diagnosis

Closing Verdict

The M135i badge spans two completely different cars - the rear-wheel-drive, straight-six purist's F20 and the front-/all-wheel-drive, four-cylinder F40. The N55 is a legend with known weak points; the B48 is more reliable but less characterful. Buy the one that matches your priorities - but buy on documented history either way.

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

→ Compare M135i 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 M135i engine prices before you buy

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Buying Checklist

Before you buy a used BMW M135i (or before you commit to an engine replacement), check these:

Cold Start

Listen for rattling or hesitation (N55: HPFP warning; B48: timing chain vigilance)

Service History

including which engine era (N55 for F20/F21, B48 for F40) and confirmed oil-interval discipline

Chargepipe Check (F20/F21)

Has the plastic chargepipe been replaced with an aftermarket metal unit?

HPFP Check (F20/F21)

Any history of long cranking, hesitation, or HPFP replacement?

Smoke Check

White smoke can indicate turbo or cooling system issues

VANOS Operation (F20/F21)

Any rough idle or hesitation at low RPM?

Engine Warning Light

Have codes been read? Any unresolved HPFP, chargepipe, VANOS, or cooling system 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.

N55B30A (3.0L Straight-Six Turbo)

Years2012–2019

Power320 PS (235 kW) @ 5,800 rpm · 450 Nm @ 1,300–4,500 rpm

2025 Enquiries- (pattern data)

Avg. Recon Cost£4,500–£7,500 [PLACEHOLDER]

Engine CodeYearsPower2025 EnquiriesAvg. Recon Cost

N55B30A (3.0L Straight-Six Turbo)2012–2019320 PS (235 kW) @ 5,800 rpm · 450 Nm @ 1,300–4,500 rpm- (pattern data)£4,500–£7,500 [PLACEHOLDER]

B48A20O1 (2.0L Four-Cylinder Turbo)2019–present306 PS (225 kW) @ 5,000 rpm · 450 Nm @ 1,800–4,500 rpm- (pattern data)£3,800–£6,500 [PLACEHOLDER]

Technical Specs

N55B30A (F20/F21)Displacement: 2,979cc · Cylinders: Straight-6 · Compression: 10.2:1 · Fuel: Direct injection · Turbo: Single twin-scroll

B48A20O1 (F40)Displacement: 1,998cc · Cylinders: 4-cylinder · Compression: 10.1:1 · Fuel: Direct injection · Turbo: Single twin-scroll

→ Compare M135i engine prices for your BMW

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Market Intelligence

Most Common Failure (F20/F21)

HPFP failure

the N55's most notorious weak point; chargepipe failure also common

Most Common Failure (F40)

Cooling system issues

less common but noted

Average Enquiry Mileage

55,000

–85,000 miles

[PATTERN DATA]

Average Replacement Cost

£4,500

–£7,500 reconditioned, supply only

[PLACEHOLDER - confirm vs cost sheet]

Most Requested Engine Code

N55B30A / B48A20O1

[PATTERN DATA]

Peak Enquiry Season

Winter

cold starts expose HPFP and VANOS issues【PATTERN DATA】

Regional Demand

London20%

South East18%

North West13%

PATTERN DATA

Regional Demand Breakdown

20%London

18%South East

13%North West

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 M135i Owners Trust BMWEngines.uk

Trusted M135i Engine Suppliers
every garage and engine rebuilder in our network is vetted, rated and reviewed by real M135i owners, as part of the Engine Finders network, across both the straight-six N55 and four-cylinder B48 eras.
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see prices, warranty terms and supply & fit options side-by-side before you commit, across every generation of this badge.
UK Engine Replacement Services for M135i
supply-only or full supply & fit available nationwide, covering every M135i generation - and we're vetted across both the F20/F21 and F40 eras.

Find the best BMW M135i engine replacement UK drivers rely on. Compare prices from trusted specialists on EnginesMarket today and get your M135i back on the road with confidence.

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No hidden fees

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12-Month Warranty

As standard

Nationwide Delivery

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