Updated April 2026 · Diesel Automotive workshop notes
The BMW N47 is one of the most-discussed diesel engines on the internet — usually for the wrong reasons. Here's the workshop view: with the right care, it'll do 200,000 miles. Without it, you'll meet us sooner than that.
The N47 chain sits at the back of the engine — between the engine block and the gearbox. To replace it, the gearbox has to come out. That's where the headline labour cost comes from.
Most N47 chains start to rattle on cold start somewhere between 80,000 and 130,000 miles. If you ignore the rattle, the chain can jump and snap, destroying the cylinder head — and at that point you're looking at cylinder head work on top of the chain job.
The fix: change the chain when the rattle starts. Don't wait. Timing chain replacement on an N47 is routine work for us.
The intake manifold has small flaps that can break off and get sucked into the engine. Result: bent valves, broken pistons, sometimes complete engine destruction. There's a known fix — a delete kit (legal in the UK because they're not emissions equipment) that removes the flaps and replaces the manifold with a non-flap version.
EGR coolers on the N47 can crack internally and dump coolant into the intake. White smoke from the exhaust, mysterious coolant loss, sometimes hydrolocking the engine. Replacement is the proper fix — see EGR repairs.
N47 injectors have a finite life — leak-back testing usually identifies the culprit. DPFs block prematurely if any of the above faults is present. Injector testing and DPF cleaning are routine.
An N47 looked after — chain done at the first sign of rattle, swirl flaps deleted before they break, EGR cooler replaced if it leaks — will easily clear 200,000 miles. We've worked on plenty over 250,000.
An N47 ignored will fail catastrophically before 150,000 — and the cost of repair at that point starts to approach the cost of a recon engine.
Got an N47 with a rattle on cold start? Get it diagnosed before it snaps. Send us your reg and we'll come back the same day. Timing chain page · Contact.
Send your reg, mileage and a description. We'll diagnose properly.