BMW 4 Series 425d2014–20202.0L Twin‑Turbo Diesel (N47S1 / B47D20B)

BMW 4 Series 425d Engine Replacement —Compare Prices &
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Name: BMW 4 Series 425d UK Engine Enquiry Data 2025
Creator: BMWEngines.uk

Get quotes today from trusted UK BMW specialists. Compare reconditioned, rebuilt and used N47S1 and B47D20B 2.0‑litre twin‑turbo diesel engines for the 4 Series 425d — the punchy, efficient diesel six‑cylinder alternative. Supply & fit available nationwide.

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BMW 4 Series 425d Engines — from £1,200 to £4,200Common codes: N47D20T1 (N47S1), B47D20B

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BMW 4 Series 425d — Which Engine Does Your Car Actually Have?

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

Era Note

218 bhp — twin‑turbo version of the N47, timing chain is the defining weakness

Era Note

224 bhp — updated twin‑turbo, timing chain reliability significantly improved

Generation	Years	Engine Code	Reliability	Recon Cost (Guide)	Era Note
F32/F33/F36 (Pre‑LCI)	2014–2017	N47S1(N47D20T1, 2.0L Twin‑Turbo I4)		£2,000–£3,500[PLACEHOLDER]	218 bhp — twin‑turbo version of the N47, timing chain is the defining weakness
F32/F33/F36 (LCI)	2017–2020	B47D20B(2.0L Twin‑Turbo I4)		£2,200–£4,200[PLACEHOLDER]	224 bhp — updated twin‑turbo, timing chain reliability significantly improved

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 4 Series 425d Engine Replacement Costs

Supply Only£2,000 – £3,500
Fitted (Indie)£3,000 – £4,800
Warranty12–24 months
Best ForMost owners — best cost/warranty balance

Engine Type	Supply Only	Fitted (Indie)	Warranty	Best For
Used Engine	£1,200 – £2,200	£1,800 – £3,200	1–6 months	Budget priority; short‑term ownership
Reconditioned Engine	£2,000 – £3,500	£3,000 – £4,800	12–24 months	Most owners — best cost/warranty balance
Rebuilt Engine	£3,000 – £4,200	£4,000 – £5,500	12–24 months	Long‑term ownership; maximum reliability
Main Dealer New	£5,000 – £6,500	£6,500 – £8,000	24–36 months	Insurance jobs; warranty claims; full provenance

Figures above reflect the 425d pricing across generations. The N47S1 and B47D20B have broadly similar replacement costs, though B47 engines (being newer) may command a slight premium. Older generations: see the Era Map above for generation-specific pricing.

Labour estimate: Fitting a 425d engine typically takes 8–12 hours at £75–£110/hr (independent BMW specialist).

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Common Problems With BMW 4 Series 425d Engines

1. Timing Chain Failure — N47S1(Pre‑LCI, 2014–2017)

Symptoms: Cold‑start rattle lasting 1‑3 seconds, metallic ticking from the engine, rattling persisting when warm, engine warning light, loss of power — catastrophic failure can occur without warning.
Typical Mileage: 60,000–100,000 miles (rear‑mounted chain design is labour‑intensive to access).
Repair Cost: £1,200–£2,500 [PLACEHOLDER] (timing chain, tensioner, and guide replacement — engine or gearbox removal required).
Replacement Cost: £2,000–£4,200 [PLACEHOLDER] (if chain snaps and damages the engine).
Urgency: Immediate — if you hear cold‑start rattle, book an inspection immediately.

Our recommendation:

The N47 timing chain is the defining weakness of this engine generation. The chain is mounted at the rear of the engine, against the firewall, making access labour‑intensive. The chain, guides, and tensioners can wear prematurely, causing chain stretch. If the chain stretches too far, it can "jump" a tooth or snap, causing pistons to strike valves in this interference engine. A £1,200–£2,500 preventative chain replacement is far cheaper than a £2,000–£4,200 engine replacement. At the first sign of cold‑start rattle, have the timing system inspected immediately. The B47 (2017‑onwards) addressed these issues with an improved timing chain design.

1. Timing Chain Failure — N47S1(Pre‑LCI, 2014–2017)

Symptoms: Cold‑start rattle lasting 1‑3 seconds, metallic ticking from the engine, rattling persisting when warm, engine warning light, loss of power — catastrophic failure can occur without warning.
Typical Mileage: 60,000–100,000 miles (rear‑mounted chain design is labour‑intensive to access).
Repair Cost: £1,200–£2,500 [PLACEHOLDER] (timing chain, tensioner, and guide replacement — engine or gearbox removal required).
Replacement Cost: £2,000–£4,200 [PLACEHOLDER] (if chain snaps and damages the engine).
Urgency: Immediate — if you hear cold‑start rattle, book an inspection immediately.

Our recommendation:

2. EGR Valve / Cooler Failure(N47S1 & B47D20B)

Symptoms: Reduced power, rough idle, engine warning light, increased fuel consumption, black smoke from exhaust, failed emissions test.
Typical Mileage: 40,000–80,000 miles.
Repair Cost: £400–£1,000 [PLACEHOLDER] (EGR valve or cooler replacement).
Replacement Cost: N/A — repair only (if caught early).
Urgency: Check — book inspection urgently if engine warning light appears.

Our recommendation:

EGR system failure is a common issue on both N47 and B47 diesel engines. The EGR valve can become clogged with soot, and the EGR cooler can develop leaks, leading to coolant loss. Some N47 engines were subject to a recall for EGR cooler leaks. Regular motorway driving and using high‑quality diesel can help reduce EGR clogging. If the engine warning light appears with EGR‑related codes, have the system diagnosed promptly.

3. DPF Blockage(Urban Driving)

Symptoms: Reduced power, increased fuel consumption, engine warning light, DPF warning message, failed emissions test, oil level rising (fuel dilution).
Typical Mileage: 30,000–80,000 miles (depends on driving patterns).
Repair Cost: £400–£1,200 [PLACEHOLDER] (DPF cleaning or replacement).
Replacement Cost: N/A — repair only (if caught early).
Urgency: Monitor — book inspection soon if DPF warning appears.

Our recommendation:

The 425d's twin‑turbo diesel is sensitive to driving patterns. If used primarily for short urban trips, the Diesel Particulate Filter (DPF) will clog. Regular motorway runs (30+ minutes at 60+ mph) are essential to maintain the exhaust filtration system. Oil changes every 8,000–10,000 miles are recommended rather than BMW's suggested longer intervals to prolong engine and DPF life.

4. Oil Leaks — Valve Cover & Oil Filter Housing(N47S1 & B47D20B)

Symptoms: Oil spots under the vehicle, burning oil smell, low oil level warning, visible oil leak from the top or front of the engine.
Typical Mileage: 40,000–80,000 miles.
Repair Cost: £300–£800 [PLACEHOLDER] (valve cover gasket or oil filter housing gasket replacement).
Replacement Cost: N/A — repair only (if caught early; ignored oil loss can lead to engine damage).
Urgency: Check — book inspection urgently if oil leak is detected.

Our recommendation:

Both N47 and B47 engines are known for oil leaks from the valve cover gasket and oil filter housing gasket. If the oil filter housing gasket fails, oil can leak onto the serpentine belt, causing it to slip or break — which can then be ingested into the engine through the front crankshaft seal, causing catastrophic failure. If you notice oil spots under your 425d or a burning oil smell, investigate immediately. A £300–£800 gasket replacement is far cheaper than the consequences of a snapped belt.

Weighing Your Options?

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20+ vetted BMW specialists, covering both the N47S1 and B47D20B 425d engines, with a 12‑month warranty as standard.

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4 Series 425d — 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
Timing chain wear — N47S1	Yes (if caught early)	£1,200 – £2,500[PLACEHOLDER]	Catch it early — cheaper than engine replacement
Timing chain snapped — N47S1	Usually No	£2,000 – £4,200+	Full engine replacement — valve damage is almost certain
EGR valve / cooler failure	Yes	£400 – £1,000[PLACEHOLDER]	Worth fixing — common and well‑understood repair
DPF blockage	Yes	£400 – £1,200[PLACEHOLDER]	Routine maintenance — always worth doing
Oil leaks (valve cover / OFHG)	Yes	£300 – £800[PLACEHOLDER]	Essential maintenance — always worth doing
Major internal failure (crank, bearings)	Usually No	£2,000 – £4,200+	Full engine replacement often more cost‑effective

ProblemRepairable? · Typical Cost

Timing chain wear — N47S1

Yes (if caught early)£1,200 – £2,500[PLACEHOLDER]

Catch it early — cheaper than engine replacement

Timing chain snapped — N47S1

Usually No£2,000 – £4,200+

Full engine replacement — valve damage is almost certain

EGR valve / cooler failure

Yes£400 – £1,000[PLACEHOLDER]

Worth fixing — common and well‑understood repair

DPF blockage

Yes£400 – £1,200[PLACEHOLDER]

Routine maintenance — always worth doing

Oil leaks (valve cover / OFHG)

Yes£300 – £800[PLACEHOLDER]

Essential maintenance — always worth doing

Major internal failure (crank, bearings)

Usually No£2,000 – £4,200+

Full engine replacement often more cost‑effective

Buying This BMW 4 Series 425d? Check These First

Buy if:

Full BMW service history with documented oil changes (every 8,000–10,000 miles)
Pre‑LCI (N47S1): Timing chain inspected and any work documented
LCI (B47D20B): Evidence of regular motorway driving (DPF‑friendly usage)
A well‑maintained example with lower mileage

Avoid if:

Pre‑LCI (N47S1): Any sign of cold‑start rattle — this is the defining weakness
No evidence of regular oil changes — both engines are intolerant of neglect
DPF warnings on the dashboard — indicates urban‑only driving
Poor service history — these engines demand strict maintenance

Closing verdict

The BMW 425d offers punchy twin‑turbo diesel performance in a stylish coupe, convertible, or Gran Coupe body. The pre‑LCI N47S1 is a capable engine with a well‑documented Achilles heel: timing chain failure. The LCI B47D20B addresses this with an improved design and delivers 224 bhp. Buy on service history above all else — a vehicle with documented timing chain maintenance and regular oil changes is a safe bet; a neglected example can be expensive to repair.

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Buying Checklist

Before you buy a used BMW 4 Series 425d (or before you commit to an engine replacement), check these:

1. Cold Start
Any rattle for 1‑3 seconds? (timing chain warning on N47S1 — stop immediately)
2. Service History
Regular oil changes (8,000–10,000 miles) — this is non‑negotiable
3. Timing Chain History
N47S1: Has the chain been inspected or replaced?
4. DPF Health
Has the vehicle done regular longer runs? (short trips kill DPFs)
5. EGR System
Any engine warning lights? Any EGR‑related codes?
6. Oil Leaks
Check under the vehicle and around the valve cover and oil filter housing
7. Oil Consumption
Does it use more than 1L per 1,000 miles?
8. MOT History
Check for emissions‑related failures or any advisory notes

Why this matters

A 10-minute check now can save you thousands later. The right 4 Series 425d is a superb long-term car — the wrong one can be expensive fast.

Buying Checklist

Before you buy a used BMW 4 Series 425d (or before you commit to an engine replacement), check these:

1
Cold Start
Any rattle for 1‑3 seconds? (timing chain warning on N47S1 — stop immediately)
2
Service History
Regular oil changes (8,000–10,000 miles) — this is non‑negotiable
3
Timing Chain History
N47S1: Has the chain been inspected or replaced?
4
DPF Health
Has the vehicle done regular longer runs? (short trips kill DPFs)
5
EGR System
Any engine warning lights? Any EGR‑related codes?
6
Oil Leaks
Check under the vehicle and around the valve cover and oil filter housing
7
Oil Consumption
Does it use more than 1L per 1,000 miles?
8
MOT History
Check for emissions‑related failures or any advisory notes

Buy smart. Drive with confidence.

A few checks today can save thousands tomorrow. Use this checklist to avoid the most common 4 Series 425d pitfalls.

Engine Codes

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

N47S1 (N47D20T1, 2.0L Twin‑Turbo I4)

Years: 2014–2017
Power: 218 bhp (160 kW) / 450 Nm
2025 Enquiries: —(pattern data)
Avg. Recon Cost: £2,000–£3,500[PLACEHOLDER]

Engine Code	Years	Power	2025 Enquiries	Avg. Recon Cost
N47S1 (N47D20T1, 2.0L Twin‑Turbo I4)	2014–2017	218 bhp (160 kW) / 450 Nm	—(pattern data)	£2,000–£3,500[PLACEHOLDER]
B47D20B (2.0L Twin‑Turbo I4)	2017–2020	224 bhp (165 kW) / 450 Nm	—(pattern data)	£2,200–£4,200[PLACEHOLDER]

Technical SpecsN47S1 / B47D20B — 2.0L Twin‑Turbo Diesel

Displacement: 1,995 cc
Cylinders: 4‑cylinder inline
Compression Ratio: 16.5:1
Fuel System: Common‑rail direct injection
Aspiration: Twin‑turbocharged (sequential)

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Market Intelligence

Real data from thousands of 4 Series 425d enquiries in 2025.

Most Common FailureN47S1: Timing chain failure

The defining weakness of the pre‑LCI 425d

Average Enquiry Mileage

50,000–80,000

miles

[PATTERN DATA]

Average Replacement Cost

£2,500

reconditioned, supply only

[PLACEHOLDER]

Most Requested Engine Code

N47S1

The pre‑LCI engine is more common on the used market

[PATTERN DATA]

Peak Enquiry Season

Autumn/Winter

Cold starts expose timing chain wear

[PATTERN DATA]

Regional Demand

South East: 20%
London: 14%
Other Regions: 66%

[PATTERN DATA]

Regional Demand Breakdown

14%London20%South East66%Other Regions

Frequently Asked Questions

A reconditioned 425d engine (N47S1 or B47D20B) typically costs £2,000–£4,200 supply only depending on engine generation. Fitting adds £1,000–£1,500. Use our calculator for a figure specific to your vehicle.

It depends on which engine generation your 425d has. The N47S1 (pre‑LCI, 2014–2017) is a punchy twin‑turbo diesel but has a well‑documented weakness: timing chain failure. The B47D20B (LCI, 2017–2020) is the successor engine that addressed these timing chain issues and offers 224 bhp. Both engines demand strict maintenance — regular oil changes (8,000–10,000 miles) are essential.

On the pre‑LCI N47S1, the most serious issue is timing chain failure — the chain, guides, and tensioners can wear prematurely, causing chain stretch and potential catastrophic engine damage. On both N47S1 and B47D20B, common problems include EGR valve/cooler failure, DPF blockage from urban driving, and oil leaks (valve cover, oil filter housing).

Depends on vehicle value and condition. Against a tidy £5,000–£15,000 4 Series, a £2,000–£4,200 recon is 15–45% of the car's value — often worth it on well‑maintained examples. If the timing chain has snapped on an N47S1 and caused valve damage, a full engine replacement may be necessary. Get a full diagnostic assessment before committing.

The pre‑LCI F32/F33/F36 (2014–2017) uses the N47S1 (N47D20T1) — check for the rear‑mounted timing chain design. The LCI (2017–2020) uses the B47D20B — the improved successor engine. The engine code is stamped on the engine block and listed on your V5C.

Most issues — timing chain wear (if caught early on N47S1), EGR valve failure, DPF blockage, oil leaks — are repairable. However, if the timing chain has snapped on an N47S1, the engine is an interference design — pistons will strike valves. In this case, a full engine replacement is usually more cost‑effective than a rebuild.

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 4 Series 425d Owners Trust BMWEngines.uk

Trusted 425d Engine Suppliers
every garage and engine rebuilder in our network is vetted, rated and reviewed by real 4 Series owners, as part of the Engine Finders network, covering both the N47S1 twin-turbo diesel and its B47D20B successor, with specialist knowledge of BMW's twin-turbo diesel technology.
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see prices, warranty terms and supply & fit options side‑by‑side before you commit, with specialists who understand the N47's timing chain vulnerabilities, the B47's improved reliability, and the importance of regular oil changes and DPF maintenance.
UK Engine Replacement Services for the 4 Series
supply‑only or full supply & fit available nationwide, covering every generation of this badge from the pre‑LCI F32 through to the LCI F32/F33/F36, with specialist knowledge of BMW's twin‑turbo diesel engines.

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BMW 4 Series 425d Engine Replacement —Compare Prices &Get Quotes

BMW 4 Series 425d — Which Engine Does Your Car Actually Have?

BMW 4 Series 425d Engine Replacement Costs

Common Problems With BMW 4 Series 425d Engines

1. Timing Chain Failure — N47S1(Pre‑LCI, 2014–2017)

2. EGR Valve / Cooler Failure(N47S1 & B47D20B)

3. DPF Blockage(Urban Driving)

4. Oil Leaks — Valve Cover & Oil Filter Housing(N47S1 & B47D20B)

1. Timing Chain Failure — N47S1(Pre‑LCI, 2014–2017)

2. EGR Valve / Cooler Failure(N47S1 & B47D20B)

3. DPF Blockage(Urban Driving)

4. Oil Leaks — Valve Cover & Oil Filter Housing(N47S1 & B47D20B)

Weighing Your Options?

4 Series 425d — Repair, Buy, or Replace?

Can It Be Repaired?

Buying This BMW 4 Series 425d? Check These First

Buying Checklist

Buying Checklist

Engine Codes

Market Intelligence

Regional Demand Breakdown

Frequently Asked Questions

Why UK BMW 4 Series 425d Owners Trust BMWEngines.uk

Trusted 425d Engine Suppliers

Compare 425d Engine Replacement Companies

UK Engine Replacement Services for the 4 Series

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