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.