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 PD (pump injector) unit is held in the cylinder head by a single side bolt. Over time the seat works itself loose: the mounting slackens, the copper ring no longer seals, and hot combustion gas blows past. First you hear a characteristic "puffing", rhythmic blowing noise from the top of the engine when cold, soot appears under the cam cover, and then the seat surface in the cylinder head erodes. At that point replacing the seal is not enough: the head has to be refurbished or replaced. It affects PD engines between 1998 and 2010, regardless of size.

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 solenoids of the mechatronics unit wear out: slow or harsh shifting, then limp mode. A characteristic sign is the partial or complete loss of reverse. Wear of the clutch pack or the wrong spring force causes jerking and slipping. Because of the wet design it fails less often and at higher mileage than the dry DQ200, but when it does fail, it is expensive.

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 PD injectors (on the 1.4, 1.9 and 2.0 TDI alike) are driven by the camshaft itself, against more than 2,000 bar. That wears the lobes and the rockers quickly: first a knocking noise, then a rough idle, hard starting and loss of power. The cause is the wrong oil: the PD engine requires a 5W-40 lubricant to the VW 505.01 specification, with PD approval. A plain synthetic is not enough, and on an everyday 5W-30 the lobes can wear through.

The Eos five piece glass hardtop is the main attraction of the model and its main risk too. The well known leak occurs on the rear edge of the roof, at the joint of the glass panel: the water gets into the rear side wall and collects under the carpet.

The vanes of the variable geometry turbo are glued together by soot and oil arriving through the EGR. First you get overboost or a lack of boost, then loss of power above 2,000 rpm, and finally limp mode. Caught in time it is enough to remove the turbo, clean it and fit a new actuator rod. Short urban trips and gentle, low rev driving speed up the deposits.

The G62 sensor tells the engine control unit how hot the coolant is. If it is faulty, the control unit thinks a warm engine is cold, and runs it rich: hard warm or cold starting, a rough idle, markedly increased fuel consumption, and a dash temperature gauge that jumps around or never reaches its usual reading. The part is cheap and can be replaced in half an hour: the trouble is that many people do not recognise it and replace an injector or a lambda sensor instead. If the fault persists, the rich mixture can destroy the catalytic converter too.

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.

The G28 sensor drops out as it heats up. While driving the car stops, then starts again after a few minutes. When warm it starts with difficulty or not at all, while cold it starts, so the workshop often cannot reproduce it. The fault code does not always stay stored either.