Toyota 1ND-TV

Toyota's 1.4-litre common-rail diesel — the D-4D of the Yaris, Auris, Corolla and Urban Cruiser, and also of the first-generation MINI One D, which took it under a supply agreement. One engine, two very different badges.

It is a small, chain-driven engine that earned a good reputation in ordinary use. The fault that defines it is the cylinder head on a defined range of production, where cracking between the valves let coolant into a cylinder — presenting as coolant loss, white smoke and eventually a failure that looks like a head gasket and is not. Toyota revised the head; build date separates an affected engine from a later one.

The other recurring items are the usual small-diesel set: injector wear producing a rough cold idle, EGR blockage, and — on cars used almost entirely for short journeys — a particulate filter that never completes regeneration. The vehicles it went into are precisely the ones bought for short urban trips, which makes duty cycle unusually relevant here.