If you own a BMW diesel built between roughly 2007 and 2015, you’ve probably heard whispers about the “BMW timing chain problem”. The whispers are correct. The N47 four-cylinder diesel — and to a lesser extent its V6 sibling the N57 — has a well-documented timing chain weakness that’s caught out an enormous number of owners. Here’s what you need to know.

Which BMW engines are affected?

The famous offenders are:

• N47 (2.0 4-cyl diesel, 2007–2014): 116d, 118d, 120d, 320d, 520d, X1, X3 (E84).
• N57 (3.0 6-cyl diesel, 2008–2017): 330d, 530d, 730d, X3 30d, X5 30d, X6 30d.
• B47 (2.0 4-cyl diesel, 2014 onwards): the N47’s successor — improved but not immune.

Why does the chain fail?

Two design choices conspire against the N47 chain in particular:

• Rear-mounted chain. The chain is at the gearbox end of the engine, not the front. This was a packaging decision to make the engine shorter. The downside: if you ever need to access the chain, the gearbox has to come out.
• Chain guides made from plastic that ages poorly. Over time the guides develop play. Chain slap follows. Wear accelerates.

Add a few short journeys (oil never gets hot, condensation builds) or extended oil change intervals, and chain wear can show up as early as 60,000 miles. The classic case is the diligently-driven N47 at 90,000–110,000 miles starting to rattle on cold starts.

The early warning signs

• Rattle on cold start — the diagnostic sign. Lasts 2–10 seconds, fades.
• Diesel knock sounds “different” — slightly hollower, a bit more “rattly” than other N47s.
• 2A87, 2A86 or 2AAF fault codes in BMW iDrive or via diagnostic scanner.
• Power dip on motorway hills.
• Mild misfire on cold start that clears.

What happens if you ignore it?

Eventually the stretched chain skips a tooth. Cam timing goes massively out. Valves contact pistons at high speed. The result is bent valves at best, broken pistons at worst — and either way, an engine that needs full replacement or rebuild.

A replacement N47 long-block runs to several thousand pounds plus fitting. A pattern reconditioned engine is cheaper but a gamble. A timely chain replacement is a fraction of either.

What’s involved in the repair?

• Remove gearbox (this is the bulk of the labour).
• Remove flywheel and rear timing cover.
• Inspect existing chain, guides, tensioner, sprockets, oil pump chain.
• Replace chain, all guides, tensioner — typically a complete kit.
• Replace rear crank seal while in there (it’s a job too).
• Replace oil pump chain (smaller chain, often forgotten).
• Refit, re-time using BMW OEM locking tools.
• Refit gearbox, refill fluids, road test, diagnostic clear.

Some workshops only replace the chain. That’s a mistake. The guides and tensioner wear together — replacing just the chain leaves you with worn guides driving a new chain, and the symptoms return inside 30,000 miles.

Should I buy an N47 BMW?

If the chain has been done recently with a full kit and OEM parts, by a specialist, with documentation — yes. They’re great cars. If the chain hasn’t been done and the car is over 70,000 miles, get the chain inspected as part of the pre-purchase inspection. We do these for £75 in our area.

What you should not do is buy an N47 with an unknown chain history and “hope for the best”. The cost of being wrong is the price of the car.

Get a fixed-price quote for an N47/N57/B47 timing chain

We do this job multiple times a week. Tell us your registration via the free estimate form, or call 01342 643 780, and we’ll come back the same working day with a fixed price. Free collection across Gatwick, Crawley, Horley, Reigate, Redhill, East Grinstead and the 15-mile radius. Mon–Sat 9 am–6 pm.

See also: BMW Timing Chain Replacement service page.