BMW N47 timing chain replacement

The N47 is the 2.0-litre four-cylinder diesel BMW fitted to the 116d, 118d, 120d, 318d, 320d, 520d and X3 20d from 2007 until the B47 replaced it around 2014–2015. Unusually, BMW put the timing chain at the back of the engine, against the gearbox. When the chain, its guides or the hydraulic tensioner wear, the chain starts to slap and you hear a rattle or whine from the rear of the engine, usually loudest at idle, when the engine is warm, or just after a cold start.

This is not a noise to live with. A stretched N47 chain can jump a tooth or snap, and when it does the pistons hit the valves. That turns a planned timing chain job into a replacement engine or a car that is no longer worth repairing. We regularly see cars that were driven for months with the rattle before the chain let go — and the difference in cost between the two is large.

Because the chain sits at the back, the engine normally has to come out of the car to replace it properly. We fit a full kit: upper and lower chains, guides, tensioner and sprockets, with new seals and gaskets where they are disturbed. Replacing only the tensioner is sometimes offered as a cheaper fix, but on a worn engine it rarely solves the rattle for long, and we will tell you honestly if we think a part-fix is a waste of your money.

Before quoting we listen to the engine, read the fault memory and check the car is a genuine N47 — the later B47 engine has a far better record. If the chain noise turns out to be something else, such as a failing dual mass flywheel or an injector knock, we tell you that instead. Call 07498 392333 or book a diagnostic check at our West Bromwich workshop on Cornwallis Road.