The N47 is BMW's most discussed diesel engine for all the wrong reasons. It delivers competitive performance and fuel economy figures, but its rear-mounted timing chain represents the most significant unaddressed systematic failure in modern BMW history. This guide covers every significant N47 fault pattern with the detail buyers and current owners need.
The N47 entered production in 2007 and was phased out in favour of the B47 from 2014 onwards. It is a 2.0 litre four-cylinder diesel available in 116d, 118d, 120d (1 Series), 316d, 318d, 320d (3 Series), 520d (5 Series), X1 18d/20d and X3 20d. The N47N designation indicates a revised version with some improvements, but the fundamental chain arrangement remains the same. If your car was made between 2007 and 2015 with a 2.0 litre diesel, check the engine code plate on the bulkhead or look up the VIN to confirm N47 or B47.
The N47 timing chain fails because of a combination of placement and design. Placing the chain at the rear of the engine means it is the last component to receive oil pressure on cold start — oil must travel from the sump, through the main galleries, through the camshaft journals, and then to the chain tensioner at the very back of the engine. In the seconds after cold start before full oil pressure builds, the chain operates without adequate tensioner pressure. Over thousands of cold starts, this produces cumulative wear on the chain links, the plastic guides, and the tensioner's ratchet mechanism. The chain stretches, the tensioner can no longer maintain correct tension, and eventually the chain begins to skip teeth. A single tooth skip can produce a catastrophic valve-to-piston collision, bending multiple valves and potentially damaging pistons. Engine rebuild cost: £3,500–7,000. Engine replacement: £2,500–5,000 for a used low-mileage unit plus fitting.
A definitive chain condition assessment requires either endoscopic inspection through the gearbox bellhousing or complete disassembly. However, several non-invasive approaches provide useful information. First: cold start rattle. Start the engine completely cold and listen carefully for a metallic rattling from the rear of the engine. The sound is similar to a diesel injector rattle but specifically from the rear — it typically lasts 5–20 seconds and then diminishes as oil pressure builds. Second: VANOS timing correlation fault codes. As the chain stretches, the camshaft timing relationship drifts. P0011, P0012, P0014, P0015 or similar camshaft timing correlation codes in the fault memory can indicate chain stretch even without audible symptoms. Third: oil service history. Engines with regular oil changes at 10,000 km or less intervals accumulate less chain wear per unit of mileage.
The N47's EGR system recirculates exhaust gases into the intake at certain load points to reduce NOx emissions. Carbon particles in the exhaust gas progressively deposit in the EGR valve, the EGR cooler and the intake manifold swirl chamber. This accumulation reduces airflow and causes the ECU to compensate with richer fuelling, increasing fuel consumption and reducing power. An EGR clean — removing, soaking and chemically cleaning the valve and cooler — costs £200–400 and should be done at 120,000–150,000 km intervals. Some N47 owners choose EGR deletion (fitting an EGR blanking plate) which eliminates carbon accumulation entirely but technically affects emissions compliance on vehicles subject to periodic emission testing.
The N47 uses a variable geometry turbocharger (VGT) where the turbine housing contains moveable vanes that control exhaust gas flow and therefore boost pressure across the RPM range. These vanes accumulate carbon deposits over time and can stick — initially causing inconsistent boost and eventually causing the actuator to fail to move the vanes at all. Symptoms include a hesitation on acceleration, unexpectedly entering limp mode under boost load, and blue smoke under hard acceleration. A vane cleaning with the turbo in-situ (force-cleaning with solvent) resolves some cases; actuator replacement costs £200–400. Full turbocharger replacement, necessary if the impeller or shaft is worn, costs £700–1,600.
Industry consensus from BMW specialists: 100,000–120,000 km on engines with regular short oil changes; 80,000–100,000 km on engines with extended oil service intervals.
Minimise driving and book a specialist inspection immediately. The chain can fail without escalation of the rattle sound.
Yes, materially. The B47 uses a front-mounted chain, improved tensioner and better oil delivery. The fundamental failure mode of the N47 does not apply to the B47.
BMW has disputed the systematic nature of the failure and addressed individual cases under warranty where applicable. No formal safety recall has been issued in most markets. Extended warranty coverage was applied to some specific builds.
Only at a price that fully reflects the cost of immediate chain replacement. Treat the chain as an immediate expense, not a future risk.
These fault cases from our database are directly relevant to this topic. Each case includes real owner descriptions, attempted repairs and outcomes.