The crankcase breather module keeps the pressure inside the engine at the right level with a membrane. On this V8 the membrane lets pressure through, and from then on the intake draws air and oil vapour out of the engine without regulation. The audible sign is a metallic whistling or grinding noise from the engine bay at idle, which typically only comes when the engine is warm, while the engine warning light is sporadically on. The engine control unit stores P2279 for an intake system leak and P0507 for a raised idle. The oil reaching the intake increases oil consumption, gives blue smoke under load, and leaves an oily film inside the intercooler. In March 2016 Audi issued a service bulletin for this (17-16-70) and named the 2013 to 2016 A6, A7 and A8 with the 4.0 TFSI engine. The factory solution is a fabric-reinforced inner membrane, meaning the breather module is replaced. The module sits between the two cylinder banks, under the intake, so the job also needs the coolant drained, and the replacement costs between 400 and 1,800 euro. The problem is reported above 100,000 km.

The four groups of parts in the air suspension (compressor, valve block, ride height sensors, air springs) work together, and any weak link causes a fault message, an uneven ride height or a car that settles. The characteristic symptom: the car sits down on one corner overnight, levels itself for minutes in the morning, and the compressor runs long and loud. According to the reports the compressor lasts 80,000 to 100,000 km; and a leaking air spring takes the compressor with it, because it keeps trying to make up the loss.

The 7 speed wet clutch S tronic used in the longitudinal engine Audis (0B5 / DL501) is more durable than the early DSG units, but the mechatronics unit is the most common source of faults here too. As the solenoids wear, the regulation of the hydraulic pressure deteriorates: harsh or missed shifts, delayed D/R engagement, and finally limp mode.