Two BMW N47 timing chain fault entries in the MyCarFault database have generated 78,808 combined views β BMW 320d E90 N47 timing chain rattle with 42,106 views and BMW 118d E87 N47 timing chain at low mileage with 36,702 views. These are among the most-read entries in the database for a single mechanical fault type, reflecting the genuine scale of this issue across the BMW owner community.
This Engine Guide guide combines structured analysis β verdicts, risk scoring and cost ranges where we have enough data β with real fault cases pulled directly from MyCarFault's reporting database, so the guidance below reflects what owners actually experience rather than manufacturer specifications alone. Background and analysis come first, followed by the linked fault reports and related guides you can jump to directly using the links above.
The N47 engineering team placed the timing chain at the rear of the engine β between the block and the gearbox bellhousing β to reduce the external dimensions of the engine bay and improve front-end crash packaging. This was a legitimate engineering decision for the packaging goals of the 1 Series and 3 Series platforms. The consequence is that the chain is the last point in the engine to receive oil pressure on a cold start. Oil flows from the sump upward through the main galleries, through the crankshaft journals, through the camshaft journals on top of the head, and then returns downward to the chain tensioner at the very back of the block. In the first 3-8 seconds of a cold start, the chain operates with the tensioner at minimum effective pressure. Over thousands of cold starts, this produces cumulative wear on the chain links, on the plastic-backed steel chain guides, and on the tensioner ratchet pawl that prevents back-travel.
The N47 cold start rattle is a metallic, rapid-fire chattering sound from the rear of the engine that is present from the moment of startup and diminishes over 5-25 seconds as oil pressure builds to the tensioner. It is not subtle β owners who have heard it describe it clearly and distinctly from the normal diesel clatter present from the front of the engine. The sound comes specifically from the rear: if you stand beside the car with the bonnet open on a cold start, the rattle comes from the firewall end of the engine rather than the front. The rattle is the chain slapping against the guides before the tensioner pressurises. Each cold start with rattle extends the wear. The chain does not necessarily rattle every start β on mild days or when the car has been used recently, oil drains back to the tensioner slowly enough to maintain some residual pressure. This intermittent character is why some owners dismiss it for months before catastrophic failure.
The MyCarFault entry BMW 118d E87 N47 timing chain failure at low mileage has 36,702 views and reflects the most alarming aspect of the N47 problem: chain failure is not exclusive to high-mileage cars. The oil delivery problem at cold start is present from the day the car leaves the factory. Engines that have experienced frequent short journeys β where the engine never fully warms up between cold starts β accumulate chain wear faster than engines used on longer runs. A BMW 118d used for school runs and short urban commutes can experience chain rattle at 70,000-90,000 km on the original chain. An equivalent engine used predominantly for motorway driving may reach 140,000 km without the same degree of wear. Mileage alone is not the correct risk assessment framework for the N47.
When the chain tensioner can no longer maintain adequate tension, the chain begins to skip teeth on the crankshaft or camshaft sprocket. A single tooth skip produces a mistimed ignition event β the piston is not where the ECU expects it to be. On a diesel engine at compression temperatures, this means fuel ignites with the piston in the wrong position. On a single skip, the result may be a misfire code and limp mode. On a multi-tooth skip or chain break, the intake valves open while the piston is rising, the piston contacts the valve stems, the valves bend or break, piston crowns are damaged and the cylinder head is destroyed. The time elapsed between normal operation and catastrophic internal damage is measured in seconds. There is no gradual degradation warning at the end stage β the transition is sudden.
The N47 2.0 litre diesel was fitted to: BMW 116d, 118d, 120d, 123d (E87, E81, F20); BMW 316d, 318d, 320d, 325d (E90, E91, E92, E93, F30, F31); BMW 520d (E60, F10); BMW X1 xDrive18d, xDrive20d (E84); BMW X3 xDrive20d (F25). Production ran from 2007 to approximately 2015, when the B47 replaced it. Any 2.0 litre BMW diesel built in this window should be assumed N47 unless the engine code is confirmed as B47 via the VIN.
A preventive N47 timing chain replacement requires either gearbox removal or engine lowering to access the rear of the block. The gearbox removal route is more common β the gearbox is unbolted from the bellhousing and moved rearward on a transmission jack to expose the chain cover. A full preventive kit includes the chain, both chain guides, the tensioner assembly, the tensioner ratchet, and the crankshaft and camshaft sprockets if wear is evident. Oil change with fresh specification oil is performed during reassembly. Labour time is 12-20 hours at a competent independent BMW specialist. Total cost range: Β£1,500-3,500 at a specialist; Β£3,000-5,500 at a main dealer.
The BMW owner community consensus, reinforced by the 78,808 combined views on these two fault entries, is unequivocal: any N47 diesel purchased without documented chain replacement should be treated as requiring immediate preventive work. The cost of a preventive chain replacement is fixed and known. The cost of a catastrophic failure is three to five times higher, plus the car is undriveable during repair. Owners who bought N47 diesels and addressed the chain proactively report years of subsequent reliable service. Owners who gambled on an unserviced chain and lost describe it as the most expensive used car mistake they made.
No formal safety recall was issued in most markets. BMW extended goodwill warranty coverage to some affected vehicles on a case-by-case basis. Owner groups in several countries attempted legal action, with varying outcomes by jurisdiction.
The N47N has a slightly revised tensioner but the fundamental rear-chain placement and oil delivery concern is unchanged. Treat N47N cars with the same scrutiny as original N47.
BMW Longlife-04 specification, typically a 5W-30 full synthetic. Change at 10,000 km maximum intervals regardless of the iDrive service indicator.
In most jurisdictions, a seller is required to disclose known faults. If chain rattle has been heard, this constitutes a known fault. Non-disclosure creates legal exposure in private sale.
Link to: /common-problems/bmw-3-series | /buying-guide/bmw-e90-worth-buying | /repair-cost/timing-chain-replacement-cost | /engines/bmw-n47-problems