The four-cylinder diesel behind the 320d — a genuinely capable, efficient engine whose reputation is dominated by one specific, well-documented failure mode that any serious buyer needs to screen for.
The timing chain on this engine is positioned at the back, against the bulkhead — the same costly-to-access design seen on some Audi and VW engines, but compounded here by a chain guide material that wears and sheds debris, leading to premature chain stretch and, in the worst cases, complete chain failure that destroys the engine. BMW revised the design partway through production, but the only reliable way to know a specific car's risk is its individual service history.
Not a guarantee, but a pattern seen consistently across owner forums and independent-garage reporting.
The window where undocumented timing chain failures have most commonly been reported.
EGR and DPF issues become more common on short-trip-only cars.
Cars with a preventative chain replacement or revised late-production chain commonly reach this point without major engine work.
This is the single most important check on any N47: ask for documented proof of the timing chain's condition, production date, or any prior replacement before considering anything else about the car.
A rattle on cold start that takes more than a second or two to settle is a meaningful warning sign — have it assessed by a specialist rather than dismissing it.
Ask about driving pattern for EGR/DPF risk, same as with other modern diesels — a motorway-biased history meaningfully lowers that specific risk.
Model-specific pages, with notes on how it behaves in that particular car.