Hyundai R-family (CRDi)

The Hyundai Motor Group's 2.0 and 2.2 litre common-rail diesel — the engine of the Santa Fe, Sorento, Tucson and Sportage, and the group's first diesel to compete directly with European designs on refinement.

The recurring failure is the timing chain and its tensioner, and the useful detail is that it announces itself audibly — a rattle on cold start from the front of the engine — well before any correlation code appears. That is the moment to act; by the time codes arrive the guides are usually already damaged.

The emissions side is the other half: EGR cooler blockage, particulate-filter regeneration failure on short-journey cars, and injector wear that presents as a rough cold idle. These engines are also widely used in markets with variable diesel quality, where fuel contamination is a more common root cause of injector failure than age is — which is worth establishing before fitting a replacement set that will fail the same way.