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 light, magnesium cased MQ200 and the MQ250, sized for higher torque, are the most widespread manual gearboxes in the transverse engine VAG models. Both have the same two weak points, and both depend on use.

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 ABS control unit fails. First the ABS and ESP lights come on intermittently, then they stay on, and the stability control drops out. The fault typically appears with code `01435`: that points at the controller of the hydraulic brake unit. The unit can often be refurbished, because the fault is in the soldering. A new controller is not always needed.

The first series Touran fails the roadworthiness test for rust more often than average, and the reports single out the tailgate. The corrosion starts along the edge and the seams, initially only as blistering paint. Added to that, oil leaks are above average on every model year and engine version, which contaminates the metal from below.

The rubber seals of the rear doors age and become porous, and the sunroof drains block up. The water gets into the rear footwell and the side wall of the boot; it stays under the carpet, so it goes unnoticed for a long time. The rear is full of electronics and trim, and the connectors corrode.

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 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.