BMW B47

The four-cylinder diesel of BMW's modular family — 500 cc per cylinder, shared architecture with the B37 three and B57 six — and the N47's replacement across the volume range.

The reason to know it is not the same engine as the N47 is the timing chain. The N47's rear-mounted chain and its expensive failure are the first thing anybody says about a BMW four-cylinder diesel, and the B47 was substantially revised in exactly that area. The reputation transfers; the fault largely does not. Establish which engine is fitted before quoting a chain job.

What it does carry is the modern emissions stack — EGR, particulate filter and AdBlue on most markets — and the EGR module on early B47s was subject to recall for a cracking and overheating risk. Check open campaigns against the VIN. Beyond that, its faults are the diesel duty-cycle faults every engine here shares: filters that cannot regenerate on short journeys, and the cascade of codes that follows.