BMW B47 Engine Problems: What Owners Need to Know
Image: BMW B47C20B complete engine with just 50K miles for sale at MT Auto Parts for £3,199.99
The B47 is BMW's answer to one of its own mistakes. When the N47 diesel developed a reputation for catastrophic timing chain failures, chains snapping at the back of the engine, behind the flywheel, turning reliable diesel cars into very expensive paperweights, BMW went back to the drawing board. The B47 engine arrived in 2014. It moved the timing chain to the front of the engine, where it belongs. It improved fuel efficiency. It met Euro 6 emissions standards. And it built a reputation as one of the better modern diesel engines in its class.
That reputation is mostly deserved. But the B47 is not without its own problems, and some of them are serious enough that anyone buying a used car with one fitted should know about them before handing over any money. This guide covers what actually goes wrong, when, and what it costs to fix.
What the B47 Is and Where It's Fitted
The B47 is a 2.0-litre, four-cylinder turbocharged diesel, the engine you'll find in the majority of BMW diesels sold since 2014. It replaced the N47 across the entire range and has been fitted to the 1, 2, 3, 4, 5 Series, X1, X3, X4, and X5 20d, as well as various Mini models. It comes in two principal variants — the B47D20A, which covers most applications from 116hp to 190hp, and the B47D20B, a higher-output version producing around 231hp in the 525d and similar models.
In the 2025 reliability survey, diesel 5 Series models, predominantly B47-powered, scored 93.9% in the executive car class. That's a solid result, particularly compared to the N47 era. But 'generally reliable' doesn't mean problem-free, and the faults that do appear on BMW B47 engines are worth understanding in detail.
The Timing Chain — Better Than the N47, But Not Without Risk
The single most important thing BMW changed between the N47 and B47 was the timing chain location. On the N47, it sat at the rear of the engine, behind the flywheel. To access it, the gearbox had to come out first. This made routine inspection essentially impossible and replacement extremely expensive, and it meant that by the time a chain was making noise, serious damage was often already underway.
The B47 moves the chain to the front. This is the industry-standard position, and it's where it should always have been. Access is vastly better, inspection is practical, and replacement, if it's needed, doesn't require gearbox removal.
On paper, this resolved the N47's most notorious weakness. In practice, the B47's timing chain is not entirely problem-free. Pre-2018 B47 engines, particularly the D20A variant built before BMW revised the tensioner specification, can develop chain rattle on cold starts if maintenance has been extended or the oil specification hasn't been followed. Independent BMW specialists report seeing tensioner wear on higher-mileage early B47s that have been serviced on BMW's long-life schedule rather than the shorter intervals the engine actually needs.
The symptoms are the same as the N47 and any other stretching chain: a metallic rattle on cold start that quietens as the engine warms up and oil pressure builds. If you buy a B47 car and hear this, investigate it before the next service. A stretched chain on a front-of-engine design is a much more accessible and affordable repair than the N47 equivalent, typically £800 to £1,400 at an independent specialist, but it doesn't get cheaper by waiting.
Post-2018 B47 engines are significantly less affected. BMW's revised tensioner design addressed the weak point, and cars built from late 2017 onwards rarely show chain-related faults before 150,000 miles with correct maintenance.
The EGR Recall — This One Really Matters
In 2018, DVSA issued recall NSC R/2018/151. It covered approximately 320,000 UK vehicles fitted with B47 engines, predominantly built between 2015 and 2017. The fault was the EGR (exhaust gas recirculation) cooler, which could crack internally, allowing hot coolant to contact soot deposits accumulated in the EGR system. The resulting mixture was identified as a fire risk.
This is not a minor service bulletin. It is a genuine safety recall, and every affected B47 car should have had the work completed, the replacement of the EGR cooler with a revised design. BMW carried out the recall at no charge.
Before buying any B47 car built between 2015 and 2018, check whether this recall has been completed. Ask for the paperwork, not just the word of the seller. Any BMW dealer can check by VIN in under two minutes. If the car has not had the recall done, factor the inconvenience of booking it into your decision, and make sure you actually book it, because this is not a fault to ignore.
EGR Valve and Intake Carbon Build-Up
The EGR recall covers the cooler, but the EGR system creates a separate ongoing maintenance issue that affects B47 engines regardless of recall status.
The EGR valve recirculates a proportion of exhaust gas back into the inlet manifold to reduce nitrogen oxide emissions. Over time, and particularly on cars used predominantly for short journeys, carbon deposits accumulate in the EGR valve, the intake manifold, and the swirl flaps that control air distribution. On city-driven cars, this process accelerates substantially because the engine never gets hot enough to burn off deposits naturally.
When the build-up becomes significant, the engine loses power, idles roughly, and the throttle response becomes sluggish. Fault codes relating to airflow and EGR deviation appear. In some cases, the swirl flap actuators fail or the flaps themselves break and send pieces of plastic into the engine, a significantly more serious fault that can cause damage requiring a new inlet manifold.
The fix for deposit build-up is chemical or mechanical cleaning of the intake system, not cheap, but considerably less expensive than the consequences of ignoring it. Preventative removal and cleaning of the EGR valve and swirl flaps at around 60,000 to 80,000 miles is a worthwhile investment on any B47 used heavily in town driving. Some independent specialists will blank off the swirl flaps during the process to prevent future actuator failures, which costs £200 to £400 and removes a potential failure point permanently.
DPF Clogging
No BMW diesel guide would be complete without covering the DPF, and the B47 is no exception. The diesel particulate filter traps soot from combustion and periodically burns it off during a regeneration cycle, a process that requires sustained driving at higher speeds to raise exhaust temperatures sufficiently.
A B47 used primarily for school runs, short commutes, and urban driving will block its DPF regularly. The first sign is a warning light. If you act on it, a 40-minute motorway run at 60 mph or above, the car can often complete a regeneration, and the light clears. Ignore it until the car goes into limp mode and you're looking at a forced regeneration at a garage, or worse, a DPF replacement. A new DPF for a B47-engined BMW costs £700 to £1,500 fitted, depending on the model.
The B47 uses the same AdBlue (selective catalytic reduction) system as other modern Euro 6 diesels. The AdBlue level needs topping up roughly every 12,000 miles. Buy it at any petrol station or motor factor; it's not expensive. Let it run out, and the car will first warn you, then refuse to start. It's a legally mandated emissions system, and the car is designed to prevent driving without it. Don't ignore the warnings.
Turbocharger
The B47's single-scroll turbocharger is generally dependable when the engine is serviced on schedule and the oil is changed at appropriate intervals. When problems do appear, they're almost always traceable to one of the same causes that affect turbos across BMW's diesel range: extended oil change intervals, the wrong oil specification, or short-journey use that prevents the engine from reaching proper operating temperature before shutdown.
On the B47D20B, the higher-output twin-turbo variant in the 525d and similar, the actuator on the high-pressure turbo is a more common fault. Independent specialists report actuator failure on these applications from around 80,000 miles, triggering limp mode and fault codes P0046 or P0047. Actuator replacement on this variant runs £900 to £1,400; a main dealer quote for a complete turbo assembly tends to be considerably more.
On standard single-turbo B47 applications, outright turbo failure before 150,000 miles is uncommon on correctly maintained engines. If you're buying a used example and the car has had regular oil changes with the correct BMW Longlife-04 specification oil, the turbo is unlikely to be an immediate concern.
The Maintenance That Prevents Most of This
The majority of B47 problems aren't design failures. They're the result of a modern, complex diesel engine being serviced on intervals that were too long, with oil that didn't meet the specification, and used for journeys that were too short to keep the exhaust system clean.
Change the oil every 7,500 miles rather than BMW's default long-life interval. Use oil that meets the BMW Longlife-04 standard, which is specifically formulated for diesel engines with DPFs and EGR systems. Give it a proper run at least once a fortnight. Check the AdBlue level. Have the EGR system inspected at 60,000 miles on any car used in urban conditions. These are not expensive interventions — they're cheaper than any single repair on this list.
A B47 with a clean service history and correct oil specification will regularly reach 150,000 to 200,000 miles without major issues. One that's been run on long-life intervals in a city will show problems considerably earlier.
Need a B47 Engine or Parts?
At MT Auto Parts, we stock used genuine BMW parts and complete used BMW B47 engines from F and G-generation models we've broken ourselves. Donor mileage is documented, every unit comes with a 30-day warranty, and we can confirm fitment against your registration before you order.
If you need a used B47 engine for sale and you're replacing it after a failure or sourcing for a rebuild, message us on WhatsApp with your car's details, or search our engines and engine parts section at mtautoparts.com.
