A disintegrating belt sheds fibres and pieces of rubber into the oil. These block the oil pick-up, the filter and the pump itself, the flow of oil drops and the engine is left without lubrication. From there the crankshaft bearings and the turbo go first, and in the end the engine can even seize.

Time matters more here than mileage. Real failures come between 60 000 and 100 000 miles, that is between roughly 96 000 and 160 000 kilometres, and at three to seven years of age. That is much earlier than the maker's original guidance, which was ten years or 150 000 miles. In 2024 the maker brought this down of its own accord to six years or 100 000 miles, and the reason given was exactly the early wear caused by oil dilution.

The belt runs in oil under the cover, so it cannot be seen from outside, and the beginning of the breakdown is hard to spot without a detailed inspection. What can be seen is the rubber particles and unusual debris appearing in the old oil drained at an oil change. The replacement, with the belts, the tensioners, the idlers and a flush of the lubrication system, costs between 1000 and 1300 pounds.

Above 200,000 km the bearings can drone and the dual-mass flywheel can knock. The oil level is worth watching, because leaks are common and the gearbox tolerates a dropping level badly.

At high mileage the synchros on the first two gears wear out, and then the shift grates. The gearbox comes with a dual-mass flywheel, which is not the most durable part either.

The escaping gas mixes the unburnt hydrocarbons with the engine oil under the rocker cover, and a hard, coal-like crust bakes out of that. This deposit surrounds the injector and over time glues it into the cylinder head.

The symptoms are easy to recognise. At idle a rhythmic chuffing noise is audible, one per combustion event. A diesel smell comes from the engine bay, and through the ventilation into the cabin as well. Black, oily deposits are visible at the base of the injector. The engine oil becomes diluted with fuel, and whitish-blue smoke can appear too.

If things are taken past this point, the carbon literally welds the injector into place, and a dedicated injector puller or a slide hammer is needed to get it out. Prying damages the body of the injector. If the seat has already been eaten away, the cylinder head has to be machined or replaced.

The quality of the repair decides matters here. A new copper washer is needed, the old one can never be reused, the seat has to be cleaned with a hand-turned seat cutter, and the torque has to follow the factory figure. Cleaning the seat is the most important step and the one most often done wrong. If one injector needs replacing, typically all four do, because their state of wear is similar, and a new one alongside worn ones does not give the right metering.

The metal dust travels on to the injectors and destroys those too, so a pump fault easily turns into a repair of the whole injection system: the system has to be flushed and the injectors replaced. The pump can also give up suddenly, even on a motorway, and the engine then stops while driving.

The injectors themselves also give up at around 200 000 kilometres, and their symptoms are easy to recognise. The most characteristic is difficult starting on a warm engine. With it comes damaged atomisation at the nozzle, a back-leak through the worn nozzle which makes starting worse still, and fuel getting into the crankcase and raising the oil level.

That last sign is the one that can be caught on the dipstick: if the oil has risen above MAX and smells of diesel, it belongs to the injection system.