N47 vs B47: Differences, Reliability & Which to Buy
Image: BMW B47D20B Complete Engine for £4,999.99 at mtautoparts.com
If you are looking at a used BMW 118d, 320d or 520d, the badge on the boot will not tell you which engine is under the bonnet. Between 2014 and 2015, BMW replaced the 2.0-litre N47 diesel with the B47 across most of its range, often midway through a model's life. Two cars with identical badges and similar registration dates can have different engines, and the difference matters.
The N47 is the engine with the timing chain reputation. The B47 is its successor, and in most respects a better engine. This guide covers what changed, where each engine still has weaknesses, and what to look for before you buy.
N47 vs B47 at a Glance
On paper, the two engines look close: same capacity, same cylinder count, same chain position. The real differences are in how they have held up in service and how much emissions equipment each carries.
The BMW N47 Engine
The N47 engine arrived in March 2007 in the facelifted E87 1 Series and went on to power almost every four-cylinder BMW diesel until 2014. In F-generation cars you will find it in the F20 and F21 1 Series, F30 and F31 3 Series, F10 and F11 5 Series, F25 X3 and early F22 2 Series, along with several MINI Cooper D and SD models.
BMW N47 engine problems: the timing chain
The N47's timing chain sits at the back of the engine, against the gearbox. When it wears, the first sign is usually a rattle from the rear of the engine, near the bulkhead, most noticeable at idle or just after a cold start. Left alone, a worn chain can jump or snap, and on a diesel that normally means bent valves and a ruined engine.
The worst-affected engines were 2.0-litre units built between 2007 and early 2009. BMW revised the chain drive, including the crankshaft sprocket, from May 2009, which reduced failures but did not end them, and reports continue on engines built up to 2011 and, less often, beyond. Because of where the chain sits, replacing it normally means taking the engine out, so a repair costs far more than on an engine with the chain at the front.
Buying an N47 car: Ask for invoices showing a timing chain replacement, and listen to the engine from cold with the bonnet open. A rattle from the gearbox end that does not settle down within a few seconds needs checking by a BMW specialist before you buy.
Other N47 weak points
Like most modern diesels, the N47 suffers from EGR and DPF problems on cars that rarely see a long run. It was also covered by BMW's 2018 EGR cooler recall in the UK, which addressed a risk of coolant leaking from the EGR cooler and igniting soot deposits. The recall and its 2019 extension covered many diesel BMWs built between 2010 and 2017, including both N47 and B47 cars, so any car you are considering should have it recorded as completed.
If you want to learn more about the BMW N47's common problems and weak points, read our full guide: Common BMW N47 Engine Problems (And How to Fix Them).
The BMW B47 Engine
The B47 engine was introduced in 2014 as part of BMW's modular engine family, which shares 500 cc per cylinder across the three-cylinder B37, four-cylinder B47 and six-cylinder B57 diesels, as well as the matching B38, B48 and B58 petrol engines. Early applications included the F10 520d, the F25 X3 and the F45 2 Series Active Tourer. The 1 and 3 Series switched over at their 2015 facelifts, and every four-cylinder diesel BMW since has used it.
Power and torque are up on the N47 at every output level, and BMW quoted fuel savings of 0.1 to 0.4 litres per 100 km depending on model. The engine has been updated several times since launch: from late 2017, many cars gained AdBlue (SCR) injection to meet tighter emissions rules, and from around 2020, many models added a 48-volt mild hybrid system. Not every B47 car has AdBlue, so check the specification of the car in front of you.
BMW B47 engine problems
The BMW B47's common problems include several issues associated with modern diesel engines. EGR valves and coolers can accumulate soot, while DPF blockages are more likely in cars used mainly for short journeys. Turbocharger wear can also become a concern, particularly when oil changes are delayed or lubrication is inadequate. Depending on the model and emissions system, later versions may also develop faults involving AdBlue components, sensors, heaters or pumps.
Timing chain wear can occur, although it should not automatically be treated as an early or inevitable failure. The chain is located at the rear of the engine, making replacement labour-intensive if it becomes necessary. As with the N47, restricted access can make this an expensive repair.
Engine oil matters: Use oil that meets the specification required for the particular B47 variant. BMW Longlife-04 applies to many versions, but the correct approval should be confirmed for the vehicle. More frequent oil changes than the maximum service interval may be beneficial, especially for cars used mainly on short journeys, helping protect the turbocharger and timing-chain system.
For a closer look at common faults, symptoms and potential repairs, read our full guide to BMW B47 engine problems.
N47 vs B47: Which to Buy?
For most buyers, the B47 is the safer choice. It has no equivalent of the N47's timing chain record, it is more economical, and it is newer. The main thing to watch is how the car has been used: a B47 that has spent its life on school runs is more likely to need DPF and EGR work than one that has covered motorway miles.
An N47 car can still be good value, especially a later F-generation example with full service history and evidence of chain work, or a car with a replacement engine already fitted. Prices reflect the engine's reputation, so you should pay less, and you should be prepared to walk away from any car that rattles.
If you need a replacement engine or parts for either, MT Auto Parts supplies used N47 and B47 engines and engine parts dismantled from F- and G-generation BMWs, with the donor car's recorded mileage and condition notes on every listing and a 30-day warranty on almost all parts (T&C apply).
FAQ Section
Is the N47 engine reliable?
It depends on which version you have and how it has been looked after. The early N47D20A, built from 2007 to early 2009, carries the highest timing chain risk, and the N47D20B that followed was improved but still vulnerable. The N47D20C, fitted to most F-generation cars from 2011, has a revised chain drive and fails far less often. Swirl flaps, EGR, DPF and turbo faults also feature, and we cover each one, with symptoms and fixes, in our guide to common BMW N47 engine problems.
Is the B47 engine reliable?
Yes, by the standards of modern diesels. B47 engine reliability is considerably better than the N47's, and there is no comparable record of early timing chain failures. Its common faults are emissions-related: EGR, DPF and, on later cars, AdBlue components. Regular oil changes and regular longer drives make most of these avoidable.
When was the BMW B47 engine introduced?
The B47 came out in 2014. Early cars to get it included the F10 520d, F25 X3 and F45 2 Series Active Tourer. Other models switched over through 2015, including the 1 and 3 Series at their facelifts, so a 2014 or 2015 car could have either engine.
Does the BMW B47 engine have timing chain problems?
Not in the way the N47 did. B47 chains can wear at high mileage, especially where oil changes have been stretched, but there is no widespread pattern of failures. Because the chain is at the rear of the engine, a replacement is still a major job if it is ever needed.
How can I tell if my BMW has an N47 or a B47?
Run the VIN through an online BMW parts catalogue such as RealOEM, which shows the engine code for that car, or have it read from the engine control unit with a BMW-capable diagnostic tool. Build date alone is not reliable during the 2014 to 2015 changeover.
Which BMW models have the N47 engine?
The N47 1.6- and 2.0-litre diesel engines were fitted to selected versions of the BMW 1-5 Series, as well as the X1, X3 and some X5 models. Check the engine code and production year for the exact application. You can also check our full guide: which BMW models have the N47 engine.
Which BMW models have the B47 engine?
Common issues include EGR valve and cooler problems, DPF blockage, carbon buildup in the intake and, less frequently, timing-chain or fuel-system faults. The likelihood of these problems depends on maintenance history, mileage and driving conditions. Read our full guide to common BMW B47 engine problems for more details.
Can a B47 replace an N47?
Not as a simple swap. The B47 uses different engine electronics, wiring and emissions hardware, so fitting one to an N47 car is a major conversion rather than an engine change. The practical route is a used or reconditioned N47 with a known history, and we compare the options and typical UK prices for how much a used BMW N47 engine costs.
Disclaimer: This article is for general information only. Engine applications, build dates, and specifications vary by market and model year. Always confirm the engine code for a specific vehicle by VIN. Any costs mentioned are indicative estimates and will vary by workshop and region. Have faults diagnosed by a qualified BMW specialist before committing to repairs.
