BMW M135i2012–present2 Engine Generations

BMW M135i Engine Replacement —Compare Prices &
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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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Supply &Fit Available
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BMW M135i Engines — from £2,500 to £10,500Common codes: N55B30A, B48A20O1

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Reconditioned
Rebuilt
Used
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The M135i Through Time — Era Map

Two generations. Two 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.

Era Note

The front-/all-wheel-drive generation — a genuinely different car under the same badge. More reliable, less character.

Generation	Years	Engine Code	Reliability	Recon Cost (Guide)	Era Note
F20/F21	2012–2019	N55B30A(3.0L Straight-Six Turbo)		£4,500–£7,500[PLACEHOLDER]	The original rear-wheel-drive M135i — a BMW purist's favourite. HPFP and chargepipe the weak points.
F40	2019–present	B48A20O1(2.0L Four-Cylinder Turbo xDrive)		£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?

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 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 Type	Supply Only	Fitted (Indie)	Warranty	Best For
Used Engine	£2,500 – £4,500	£3,500 – £5,800	1–6 months	Budget priority; older F20 examples
Reconditioned Engine	£3,800 – £7,500	£5,000 – £9,000	12–24 months	Most owners — best cost/warranty balance
Rebuilt Engine	£5,500 – £9,500	£6,800 – £11,000	12–24 months	Long-term ownership; 3+ year horizon
Main Dealer New	£8,500 – £14,000	£10,000 – £16,000	24–36 months	Insurance 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).

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Common Problems With BMW M135i 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
Urgency: 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 /failures/n54-high-pressure-fuel-pump

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
Urgency: Check — book inspection urgently

Our recommendation:

Read the full HPFP failure guide /failures/n54-high-pressure-fuel-pump

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
Urgency: 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 /failures

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
Urgency: 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 /failures/vanos-solenoid-failure

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M135i — 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
HPFP failure (N55)	Yes	£600 – £1,200	Well-understood fix; cheaper than engine replacement
Chargepipe failure (N55)	Yes	£300 – £600	Aftermarket metal unit solves permanently
VANOS solenoid wear (N55)	Yes	£200 – £500	Simple repair; part of routine maintenance on higher-mileage examples
HPFP failure (B48)	Yes	£500 – £1,000	Less common than N55 but still possible
Snapped timing chain	Usually No	£3,800 – £9,500	Typically requires full engine replacement

ProblemRepairable? · Typical Cost

HPFP failure (N55)

Yes£600 – £1,200

Well-understood fix; cheaper than engine replacement

Chargepipe failure (N55)

Yes£300 – £600

Aftermarket metal unit solves permanently

VANOS solenoid wear (N55)

Yes£200 – £500

Simple repair; part of routine maintenance on higher-mileage examples

HPFP failure (B48)

Yes£500 – £1,000

Less common than N55 but still possible

Snapped timing chain

Usually No£3,800 – £9,500

Typically 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.

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Buying Checklist

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

1. Cold Start
Listen for rattling or hesitation (N55: HPFP warning; B48: timing chain vigilance)
2. Service History
Including which engine era (N55 for F20/F21, B48 for F40) and confirmed oil-interval discipline
3. Chargepipe Check (F20/F21)
Has the plastic chargepipe been replaced with an aftermarket metal unit?
4. HPFP Check (F20/F21)
Any history of long cranking, hesitation, or HPFP replacement?
5. Smoke Check
White smoke can indicate turbo or cooling system issues
6. VANOS Operation (F20/F21)
Any rough idle or hesitation at low RPM?
7. Engine Warning Light
Have codes been read? Any unresolved HPFP, chargepipe, VANOS, or cooling system issues?
8. MOT History
Check for emissions-related failures

Why this matters

A 10-minute check now can save you thousands later. The right M135i is a superb long-term car — the wrong one can be expensive fast.

Buying Checklist

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

1
Cold Start
Listen for rattling or hesitation (N55: HPFP warning; B48: timing chain vigilance)
2
Service History
Including which engine era (N55 for F20/F21, B48 for F40) and confirmed oil-interval discipline
3
Chargepipe Check (F20/F21)
Has the plastic chargepipe been replaced with an aftermarket metal unit?
4
HPFP Check (F20/F21)
Any history of long cranking, hesitation, or HPFP replacement?
5
Smoke Check
White smoke can indicate turbo or cooling system issues
6
VANOS Operation (F20/F21)
Any rough idle or hesitation at low RPM?
7
Engine Warning Light
Have codes been read? Any unresolved HPFP, chargepipe, VANOS, or cooling system 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 M135i pitfalls.

Engine Codes

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

N55B30A (3.0L Straight-Six Turbo)

Years: 2012–2019
Power: 320 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 Code	Years	Power	2025 Enquiries	Avg. Recon Cost
N55B30A (3.0L Straight-Six Turbo)	2012–2019	320 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–present	306 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

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Market Intelligence

Real data from thousands of M135i enquiries in 2025.

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]

Most Requested Engine Code

N55B30A / B48A20O1

[PATTERN DATA]

Peak Enquiry Season

Winter

Cold starts expose HPFP and VANOS issues

[PATTERN DATA]

Regional Demand

London: 20%
South East: 18%
North West: 13%
Other Regions: 49%

[PATTERN DATA]

Regional Demand Breakdown

20%London18%South East13%North West49%Other Regions

Frequently Asked Questions

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.

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. Neither is a disaster; both demand good maintenance.

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.

Depends on vehicle value and which generation. Against a well-kept £18,000 F20, a £6,000 recon is 33% — worth it for the right car. 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.

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.

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.

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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BMW M135i Engine Replacement —Compare Prices &Get Quotes

The M135i Through Time — Era Map

BMW M135i Engine Replacement Costs

Common Problems With BMW M135i Engines

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

2. Chargepipe Failure — N55(F20/F21)

3. VANOS Solenoid Wear — N55(F20/F21)

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

2. Chargepipe Failure — N55(F20/F21)

3. VANOS Solenoid Wear — N55(F20/F21)

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M135i — Repair, Buy, or Replace?

Can It Be Repaired?

Buying This M135i? Check These First

Buying Checklist

Buying Checklist

Engine Codes

Market Intelligence

Regional Demand Breakdown

Frequently Asked Questions

Why UK BMW M135i Owners Trust BMWEngines.uk

Trusted M135i Engine Suppliers

Compare M135i Engine Replacement Companies

UK Engine Replacement Services for M135i

BMW M135i Engine Replacement —Compare Prices &
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