🟡 BMW 320d E90 N47 timing chain rattle — catastrophic failure risk

A rattling noise from the rear of the engine on cold start that may disappear once oil pressure builds. This is the classic symptom of the notorious BMW N47 timing chain fault. The N47 engine has the timing chain at the rear (flywheel end), making replacement extremely labour intensive and expensive. The plastic chain guides and tensioner fail, leading to chain stretch. If ignored, the chain snaps and destroys the engine. Immediate inspection is required — do not delay.