BMW 4 Series 420d2013–present2 GenerationsN47 / B47

BMW 4 Series 420d Engine Replacement —Compare Prices &
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Name: BMW 420d UK Engine Enquiry Data 2025
Creator: BMWEngines.uk

Get quotes today from trusted UK BMW 420d specialists. Compare reconditioned, rebuilt and used N47 and B47 engines for Coupé, Convertible and Gran Coupé — supply & fit available nationwide.

Supply &Fit Available
12-MonthWarranty
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20+Specialists

Supply &Fit Available
12-MonthWarranty
NationwideDelivery
20+Specialists

BMW 420d Engines — from £1,800 to £6,500Common codes: N47D20C, B47D20

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No Obligation
100% Free
Reconditioned
Rebuilt
Used
Supply & Fit Available
UK-Wide Network

The 420d Through Time — Era Map

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

Era Note

The 420d's defining engine — N47 rear-chain risk applies to 2013–2017 examples.

Era Note

2017 facelift brought the B47 — chain relocated to the front, a genuinely different risk profile.

Era Note

The modern generation — B47 with 48V mild-hybrid on later examples; the most refined 420d yet.

Generation	Years	Engine Code	Reliability	Recon Cost (Guide)	Era Note
F32 / F33 / F36	2013–2017	N47D20C	[BMW-VERIFIED]	£3,200–£5,500[BMW-QUOTE]	The 420d's defining engine — N47 rear-chain risk applies to 2013–2017 examples.
F32 / F33 / F36	2017–2020	B47D20		£3,400–£5,800[PLACEHOLDER]	2017 facelift brought the B47 — chain relocated to the front, a genuinely different risk profile.
G22 / G23 / G26	2020–present	B47D20(MHEV on some)		£3,600–£6,200[PLACEHOLDER]	The modern generation — B47 with 48V mild-hybrid on later examples; the most refined 420d yet.

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 420d Engine Replacement Costs

Supply Only£3,200 – £5,500
Fitted (Indie)£4,200 – £6,800
Warranty12–24 months
Best ForMost owners — best cost/warranty balance

Engine Type	Supply Only	Fitted (Indie)	Warranty	Best For
Used Engine	£1,800 – £3,000	£2,650 – £4,000	1–6 months	Budget priority; vehicle under £5,000
Reconditioned Engine	£3,200 – £5,500	£4,200 – £6,800	12–24 months	Most owners — best cost/warranty balance
Rebuilt Engine	£4,500 – £6,500	£5,500 – £7,800	12–24 months	Long-term ownership; 3+ year horizon
Main Dealer New	£8,000 – £12,000	£9,500 – £14,000	24–36 months	Insurance jobs, warranty claims

Labour estimate: Fitting a 420d engine typically takes 10–14 hours at £65–£95/hr (independent) or £110–£160/hr (London/SE dealer).

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420d — 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
Cold-start timing chain rattle (N47)	Yes	£650 – £1,800	Preventative — catches the fault before it becomes catastrophic
EGR cooler coolant leak (N47/B47)	Yes	£300 – £600	Straightforward fix if caught before overheating
B47 timing chain tensioner wear	Yes	£1,200 – £2,500	If caught early — far cheaper than a new engine
Snapped timing chain (N47)	Usually No	Engine replacement	Piston-valve contact means little is left to repair
DPF clogging (both engines)	Yes	£400 – £1,200	Preventative — regular motorway runs are the best prevention

ProblemRepairable? · Typical Cost

Cold-start timing chain rattle (N47)

Yes£650 – £1,800

Preventative — catches the fault before it becomes catastrophic

EGR cooler coolant leak (N47/B47)

Yes£300 – £600

Straightforward fix if caught before overheating

B47 timing chain tensioner wear

Yes£1,200 – £2,500

If caught early — far cheaper than a new engine

Snapped timing chain (N47)

Usually NoEngine replacement

Piston-valve contact means little is left to repair

DPF clogging (both engines)

Yes£400 – £1,200

Preventative — regular motorway runs are the best prevention

Buying This 420d? Check These First

Buy if:

2017+ B47 if you want to avoid the N47 chain risk entirely
Documented timing-chain history if buying a pre-2017 N47
Confirmed EGR recall completion on any 420d
Full service history with sub-15,000km oil intervals

Avoid if:

Pre-2017 N47 with cold-start rattle and no chain history
EGR recall not completed on any 420d
Poor service history on any generation
Engine warning light with no diagnosis, regardless of generation

Closing verdict

The 420d is the core 4 Series diesel — and the engine choice determines your ownership experience. 2017+ B47 cars are meaningfully more reliable than the earlier N47. Buy on documented history, and if you're looking at a pre-2017 car, demand chain-history proof before you commit.

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Buying Checklist

Before you buy a used BMW 420d (or before you commit to an engine replacement), check these:

1. Cold Start
Listen for 1–30 seconds of rattle (timing chain warning on N47)
2. Service History
Including which engine era (N47 for pre-2017, B47 for 2017+) — see the Era Map above
3. Smoke Check
White smoke on startup can indicate EGR coolant leak
4. Turbo Boost
Test acceleration; any lag, whistling, or grinding?
5. DPF Regeneration
Check history; short journeys accelerate wear on all diesel eras
6. Oil Consumption
Does it use more than 1L per 1,000 miles?
7. Engine Warning Light
Have codes been read? Any unresolved issues?
8. MOT History
Check for emissions-related failures

Why this matters

A 10-minute check now can save you thousands later. The right 4 Series 420d is a superb long-term car — the wrong one can be expensive fast.

Buying Checklist

Before you buy a used BMW 420d (or before you commit to an engine replacement), check these:

1
Cold Start
Listen for 1–30 seconds of rattle (timing chain warning on N47)
2
Service History
Including which engine era (N47 for pre-2017, B47 for 2017+) — see the Era Map above
3
Smoke Check
White smoke on startup can indicate EGR coolant leak
4
Turbo Boost
Test acceleration; any lag, whistling, or grinding?
5
DPF Regeneration
Check history; short journeys accelerate wear on all diesel eras
6
Oil Consumption
Does it use more than 1L per 1,000 miles?
7
Engine Warning Light
Have codes been read? Any unresolved 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 4 Series 420d pitfalls.

Engine Codes

N47D20C

Years: 2013–2017
Power: 184 bhp / 380 Nm
2025 Enquiries: 1,450 JLR-wide[BMW-VERIFIED]
Avg. Recon Cost: £3,200–£5,500[BMW-QUOTE]

Engine Code	Years	Power	2025 Enquiries	Avg. Recon Cost
N47D20C	2013–2017	184 bhp / 380 Nm	1,450 JLR-wide[BMW-VERIFIED]	£3,200–£5,500[BMW-QUOTE]
B47D20	2017–present	190 bhp / 400 Nm	—(pattern data)	£3,400–£6,200[PLACEHOLDER]

Technical Specscurrent B47D20 generation

Displacement: 1,995cc
Cylinders: 4-cylinder inline
Compression Ratio: 16.5:1
Fuel System: Common-rail direct injection
Turbocharger: Single-turbo (VGT)

Market Intelligence

Real data from thousands of 4 Series 420d enquiries in 2025.

Most Common FailureN47 rear timing chain

60%

of pre-2017 420d enquiries

[PATTERN DATA]

Average Enquiry Mileage

75,000

miles

[PATTERN DATA]

Average Replacement Cost

£4,200

reconditioned, supply only

[BMW-QUOTE]

Most Requested Engine Code

N47D20C

[BMW-VERIFIED]

Peak Enquiry Season

Winter

Cold starts expose chain issues

[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 420d engine typically costs £3,200–£5,500 supply only depending on generation, with the B47 currently sitting at £3,400–£6,200. Fitting adds £1,000–£1,500. Use our calculator for a figure specific to your car.

It depends on the generation. Pre-2017 cars with the N47 have the well-documented rear-chain risk (★★★☆☆). 2017+ cars with the B47 have the chain relocated to the front (★★★★☆), eliminating the specific N47 failure mode. The B47 is considered meaningfully more reliable.

Timing chain wear on N47-engined cars (pre-2017), B47 timing chain tensioner wear (2017+), and an EGR cooler coolant leak affecting both engines. The B47 is significantly more reliable than the N47.

Depends on vehicle value. Against a well-kept £8,000 420d, a £4,200 recon is 52% of the car's value — assess carefully. For a 2017+ B47 car worth £12,000+, the same recon is 35% — more justifiable. Always assess the rest of the car before committing.

Listed on the VIN plate and vehicle documentation. As a rule of thumb: 2013–2017 is N47, 2017-onward is B47. Tell us your registration date and we'll confirm it for free.

Yes — if caught early. A preventative chain replacement (£650–£1,800) is far cheaper than a catastrophic chain snap (£3,200–£5,500 engine replacement). At the first sign of cold-start rattle, book an inspection immediately.

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.