CDNB engine faults.

The EA888 engines built between 2008 and 2011 got a 1.5 mm oil scraper ring instead of a 2 mm one, and the 0.3 mm drain holes in that ring soot up and then block. From there the oil cannot get back to the crankcase, so it reaches the combustion chamber and burns: the reported consumption is one litre every 800 to 1,000 km, which means the oil level warning comes on before the service interval ends. The consumption can start around 60,000 km. In October 2013 Audi issued a separate service bulletin for this (17-13-42) and named the affected range: the 2009 to 2011 A4, the 2010 to 2011 A5 and A5 Cabriolet, and the 2011 Q5 with the 2.0 TFSI engine. The same document states that metro use, meaning frequent stops and long idling, raises the consumption further. In the United States a class action was filed over this and closed with a settlement, after which the franchised dealers repaired cars with the CAEB engine free of charge. The work goes as far as the pistons and costs between 2,000 and 5,000 euro.

The combined housing of the water pump and the thermostat is plastic, and it is bolted directly to the hot engine block. The many heat and cool cycles warp it, it becomes brittle, and then it develops a hairline crack: the fault is almost always the housing, not the pump itself. The signs are slowly disappearing coolant with no visible puddle, the coolant level light, a sweet smell from the engine bay, and later a pink stain under the car. The repair means replacing the pump and the housing together, and the intake manifold has to come off for it: 4 to 6 hours of work. It shows up on model years 2015 to 2025.

With direct injection the fuel does not wash the intake valves: the petrol goes into the cylinder, not behind the valve. The oil mist and soot arriving through the EGR and the crankcase ventilation therefore build up on the valve stem and head, and from 80,000 to 100,000 km they restrict the flow. Symptoms are hesitation, loss of power, a rough cold start and misfire. It is not a part failure: it is a consequence of the design, and therefore it comes back. Cleaning (walnut or dry ice blasting) helps for a few tens of thousands of kilometres.

The crankcase breather carries the vapour that forms inside the engine back to the intake, and a rubber membrane regulates the pressure. Oil and heat harden this membrane until it tears, and from then on the intake draws air through the hole in it. The engine control unit does not measure that air, so the mixture goes wrong: the engine shakes at idle, stumbles when accelerating, and the fault memory gets P2279 for an intake system leak. In the other direction oil starts towards the intake, which leaves an oily film in the intercooler and on the intake pipe and speeds up the carbon build-up on the intake valves. The audible sign is a whistling or hissing noise from the engine bay, loudest at idle. The tear is reported between 60,000 and 90,000 km. On the first and second generation the breather is a separately replaceable valve (factory number 06H 103 495 AK) and costs between 80 and 400 euro; from the third generation it is built into the cam cover, so there the cover is replaced. The maker issued three versions up to 2016, and fitting the pressure variant that does not belong to the engine brings the same symptom back.