The EGR cooler cools the recirculated exhaust gas before it enters the intake again, and coolant flows through it while it does so. The temperature difference between the two sides is large, so the wall can crack or the gasket can let through, and then the coolant reaches the exhaust or the intake side. This leaves no puddle under the car and the place of the leak is not visible from outside: the coolant evaporates and the level drops slowly, over weeks. The accompanying signs are whitish smoke, a rising coolant temperature, raised pressure in the cooling system and a sweetish smell. If it goes on for months the cylinder head can be damaged too, because the cooling gradually gets worse. On the EA189 engines the fault code P2425 usually comes with it. The problem is reported above 100,000 km, and replacing the cooler costs 600 to 1,500 euro.

The balance shaft module drives the oil pump through a hexagonal shaft stub. That hex and its mating part gradually round off, until the shaft finally turns freely: the oil pump stops and the oil pressure is gone. The process gives no warning, and that is exactly what makes it dangerous. The failure typically happens at high revs, and the oil pressure light comes on only once the damage is already done. The factory hex is undersized, so it knocks against the wall of the bore, and the wear accelerates itself. The maker classed it as a "tolerance deviation" and, given the small number of cases against total production, did not recommend preventive repair; Audi alone ran a service action (13D7). The replacement is expensive: on the German market the module replacement is 1,300 to 1,700 euro, and an independent repair touching only the hex is around 650 euro. The reported cases cluster around the Passat B6, Sharan, Audi A4/A6, Superb and Alhambra, in model years between 2005 and 2009. This layout is not only on the pump-injector (PD) engines, it is on the common rail EA189 engines too: the same module, the same hex, the same wear. The failure is typically reported between 100,000 and 160,000 km. The first sign is a short flash of the oil pressure light, in a long bend or a few seconds after a cold start, and then quiet again. The versions without balance shafts (BKD, BMM, BMN, AZV) drive the oil pump differently and are not affected by this wear. If the light stays on or flashes, stop as soon as it is safe, switch the engine off, and do not restart it until the oil pressure has been measured.

The EGR valve and its cooler block up with soot and oily deposits; the particulate filter cannot regenerate on short urban trips. The signs are reduced power, a warning light, and frequent regeneration. The software update after the diesel emissions affair made the EGR operate more often, which accelerated the phenomenon: the maker gave goodwill repairs in several cases.

The Haldex clutch engages the rear axle when the front wheels slip. The pre-charge pump blocks up with oil sludge, and the rear axle simply gets no drive: the car appears to run faultlessly as long as grip is good. The telltale sign is the front wheels spinning while the rears stand still. The same unit sits in the Tiguan I and the Passat B8 4Motion. The fourth generation Haldex, built up to October 2013, has a replaceable filter; the fifth generation after it does not, and there the oil change is the maintenance. Prevention is cheap, the consequence is not: replacing a neglected unit is a major expense.

The seven speed, wet clutch DQ500 is the DSG of the high torque models (Transporter, Arteon, Tiguan). On a heavy vehicle, on the T5 vans, the splined joint of the differential can shear. Clutch debris blocks the valves of the mechatronics unit, and it jerks on shifts. The pressure sensors fail at around 100,000 to 150,000 km, and then either the even or the odd gears drop out. The control board fails from overheating next to a clogged heat exchanger. It is not repairable, only replaceable.

The internal springs of the flywheel tire, and the two discs knock against each other. The signs are a rattling or knocking from the bellhousing at idle and when releasing the clutch pedal, and vibration through the floor. If the clutch slips without a burnt smell, that also points to the flywheel. It is worth replacing in time: a disintegrated flywheel can destroy the bellhousing too. At a clutch replacement the two go together anyway.

The springs, dampers and control arm bushes wear far earlier than average. In the roadworthiness test the suspension failure rate on this model is many times the average: the TUV statistics have shown this for years. Symptoms: knocking on uneven roads, less confident cornering, uneven tyre wear. A broken spring also occurs, typically on overloaded cars.

Waves and grooves appear on the surface of the brake discs under 30,000 km, accompanied by pulsing felt through the steering wheel and the brake pedal when braking. The phenomenon is not a question of driving style: it is traced back to faulty production batches. VW sometimes contributed to the cost as a goodwill gesture, but rejected many claims. A full brake overhaul is a substantial item.

The water channel around the roof is plastic and the support frame is steel; the two expand differently, and a stress crack forms where they meet. Add to that a rear drain squashed during assembly. The water gets onto the headlining, and from there into the cabin and the electronics. The repair is often not durable: the workshop seals it or cleans a drain, and months later it comes back.

The dash shows "Error: Workshop! Only leave vehicle in position P" with an audible warning. The message appears in whatever language the car is set to, for example "Fehler: Werkstatt! Fahrzeug nur in Stellung P verlassen" in German.