Is it worth replacing the engine in a BMW 4 Series 420d-

A 2013-2015 420d is typically worth £3,780-£12,600. If your car is worth under £5,000, a used engine replacement is usually the most cost-effective route. For cars worth over £8,000, a reconditioned or rebuilt engine with warranty is a sound investment - especially if you plan to keep the car for 2+ years.

How long does a BMW 4 Series 420d engine replacement take-

Supply-only engines are typically dispatched within 1-2 working days. Full supply & fit through a specialist workshop usually takes 2-3 days, depending on workshop availability and the complexity of the specific 420d variant (xDrive models may take slightly longer).

What's the difference between the BMW 420d and 425d engine-

The 420d uses a 2.0-litre four-cylinder diesel producing 184-190hp. The 425d uses the same 2.0-litre B47D20B engine but with a twin-turbo setup producing 224hp. While both are 2.0-litre diesels, the 425d's additional turbo and higher output mean different engine codes and compatibility.

Can I replace my N47 engine with a B47 in my BMW 420d-

Yes - the B47D20A is a direct replacement for the N47D20C in the 420d, as both engines share the same mounting points and transmission compatibility. Upgrading to a B47 offers improved reliability (revised timing chain design) and Euro 6 emissions compliance. Always verify compatibility via VIN check before ordering.

BMW 420d SPECIALISTS

BMW 4 Series 420d Engine Replacement Compare Prices & Get Quotes

Q: Which BMW 4 Series 420d engines have timing chain problems-

The N47D20C engine fitted to 420d models from 2013-2015 has a well-documented timing chain weakness. The rear-mounted chain can stretch over time, particularly with extended oil service intervals. The later B47D20A engine (2015 onwards) addressed this issue with a revised front-chain design and is significantly more reliable.

Need a replacement engine for your BMW 4 Series 420d- Get quotes today from trusted UK BMW 420d engine specialists and compare prices on reconditioned, rebuilt and used engines for your 420d Coupe, Gran Coupe or Convertible.

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BMW 4 Series 420d Engine

from£1,800 to £5,500

Usedfrom £1,800
Reconditionedfrom £2,800
Common codesN47D20C, B47D20A

BMW 4-seriesUsed Engine — N47D20C

BMW 4-series 420d Reconditioned Engine — N47D20C

BMW 4-seriesReconditioned Engine — N47D20C

BMW 4-series 420d Rebuilt Engine — N47D20C

BMW 4-seriesRebuilt Engine — N47D20C

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How it works

3 Simple Steps to Finding the Right Replacement Engine

Clear information first, then the right engine and specialist for your exact vehicle.

Variant History

BMW 4 Series 420d Engine History & Specs at a Glance

The BMW 420d joined the 4 Series range at launch in 2013 as the entry-level diesel, offering a compelling blend of economy and performance. Over its production run, the 420d underwent a crucial engine change from the N47 to the more robust B47, addressing reliability concerns and meeting tightening emissions standards.

2013
N47D20C, 2.0-litre turbo-diesel, 184hp - original 420d engine for F32/F33/F36 chassis
2015
B47D20A, 2.0-litre turbo-diesel, 190hp - Euro 6-compliant successor to the N47, introduced as part of the Life Cycle Impulse (LCI) for the 4 Series range
2020
420d receives 48V mild-hybrid technology as part of the G22 generation launch, improving efficiency and low-end response

Every engine fitted to the BMW 4 Series 420d is covered below, with UK rebuilt pricing and known failure points.

Engine Codes & Pricing

BMW 4 Series 420d Engine Codes Specifications & Replacement Cost

Find your exact engine code, specs and UK replacement cost guide.

N47D20C — 2.0L Diesel (2013-2015)

Power Output: 184hp
Years Fitted: 2013-2015

Can’t find your exact engine code?-> Get quotes for N47D20C BMW 4 Series 420d engine replacement

-> Get quotes for N47D20C BMW 4 Series 420d engine replacement

Common failure points and repair options

Timing Chain Failure

Affected: BMW 4 Series 420d (N47D20C, 2013-2015)
Typical failure mileage: 60k-120k

Root cause

The N47's rear-mounted timing chain design uses components that stretch over time, particularly where oil service intervals have been extended. A rattling noise from the rear of the engine on cold start is the primary warning sign.

Repair options

Repair tier	Dealer price	Specialist price
Timing chain replacement (preventative)	£2,200+	£1,200-£1,800
Full Replacement - rebuilt/reconditioned engine	£5,000-£8,000	£4,500-£6,500

Our recommendation

If you hear the tell-tale cold-start rattle and act quickly, a timing chain replacement (preventative) is the most cost-effective option. If the chain has already snapped or engine damage is extensive, replacement with a rebuilt B47D20A unit (with its improved chain design) is the smarter long-term play.

-> Compare rebuilt N47D20C BMW 4 Series 420d engine prices

EGR Cooler Failure

Affected: BMW 4 Series 420d (B47D20A, 2015-present)
Typical failure mileage: 60k-120k

Root cause

The EGR cooler can develop internal leaks, allowing coolant to enter the exhaust system. BMW issued a recall for this issue.

Repair options

Repair tier	Dealer price	Specialist price
EGR cooler replacement	£900-£1,500	£600-£1,200
Full Replacement - rebuilt/reconditioned engine	£5,000-£7,000	£3,800-£5,800

Our recommendation

Address EGR cooler issues promptly - the repair is relatively straightforward and far cheaper than a full engine replacement. Always check if your car is covered by the BMW recall.

-> Compare rebuilt B47D20A BMW 4 Series 420d engine prices

Don't Let Engine Failure Write Off Your BMW 4 Series 420d

Whether you're dealing with N47 timing chain failure or B47 EGR cooler issues, early diagnosis is key. A rebuilt engine through EnginesMarket comes with upgraded components addressing the original failure point, a minimum 12-month warranty, and nationwide delivery or supply & fit options - often at a fraction of main dealer prices.

Compare BMW 4 Series 420d Engine Replacement Prices Now ->

FAQ

BMW 4 Series 420d Engine ReplacementFrequently Asked Questions

Everything BMW 4 Series 420d owners usually ask before choosing a rebuilt, reconditioned or used replacement engine.

A replacement engine for a BMW 420d typically costs between £1,800 and £6,500 depending on condition【EM-QUOTE】. Used N47D20C units start from around £1,800, while reconditioned units range from £2,800 to £5,500. Rebuilt engines with warranty sit at £3,800-£6,500. Specialist fitting adds approximately £650-£910 in labour【EM-QUOTE】.

Used: £1,800-£3,200
Reconditioned: £2,800-£5,500
Rebuilt: £3,800-£6,500

-> Get a precise quote for your BMW 420d

The N47D20C engine (fitted to 420d models from 2013-2015) has a well-documented timing chain weakness. The rear-mounted chain can stretch over time, particularly with extended oil service intervals. The later B47D20A engine (2015 onwards) addressed this issue with a revised front-chain design and is significantly more reliable.

N47D20C: timing chain stretch risk - listen for cold-start rattle
B47D20A: EGR cooler issues - recall applied, timing chain issues rare

-> Check your 420d's engine code

Why Choose Us

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Comparing quotes for your BMW 4 Series 420d engine replacement is completely free and carries no obligation. Enter your registration above to get matched with vetted UK specialists who stock the exact engine for your 420d - whether you need used, reconditioned or rebuilt, with supply-only or full fitment options.

1,450+1,450+ BMW 4 Series engines supplied through our network【EM-VERIFIED】

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