4 Series
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Which Bmw 4 Series engine is the most reliable? See common problems, reviews and reliability verdicts across generations and engines.
Frequently asked questions
Which Bmw 4 Series engine is the most reliable?
420d / 430d (B47 / N47 / B57 diesel) — Maint. Sensitive verdict. The diesels span the early 2.0 N47 (F32 — carries the notorious rear-mounted-timing-chain wear that's labour-heavy to fix) and the later 2.0 B47 (the much-improved replacement, shared with the 3/5-Series and X-models), plus the smooth 3.0 straight-six B57/N57 (430d). The B47 is the one to buy: it fixed the N47's chain reputation. Standard modern-diesel cautions remain: DPF and EGR on short trips (EGR cooler a known weak point), injector attention, and AdBlue on later cars. The straight-six 430d is a superb, durable long-distance engine. Buy on chain (avoid a rattly N47), EGR and DPF history.
Which Bmw 4 Series engines should you avoid?
None of the Bmw 4 Series engines listed are rated "Problematic" or "Avoid" — but always check the service history before buying.
What are the most common Bmw 4 Series problems?
The most commonly reported problems across all Bmw 4 Series generations and engines: N47 rear timing chain (early), EGR cooler / DPF / AdBlue, Timing chain (N20 early) / carbon, VANOS / PCV / turbo coolant.