2009 Audi S5 Problems: 5 Known Issues

On the 2008-2012 Audi S5 4.2L FSI V8 (CAUA), the B8 S5's 4.2L FSI V8 uses low-tension oil control rings that coke up with carbon over time, letting oil past the rings and into the combustion chamber. Owners report burning roughly a quart every 1,000-3,000 miles, and in advanced cases the trapped carbon and oil dilution lead to cylinder wall scoring. This is a piston/ring design issue specific to the naturally aspirated 4.2 FSI V8 in the 2008-2012 S5 coupe - it is a different failure from oil consumption on the later 3.0T supercharged cars. Audi's earlier oil-consumption settlement activity covered other engines, so 4.2 owners have generally paid out of pocket.

On the 2008-2025 Audi S5, the S5 suffers from carbon deposits on the intake valves, a problem common to all Audi direct-injected engines. The performance-oriented tuning makes power loss from carbon more noticeable than in base models.

On the 2008-2012 Audi S5 4.2L FSI V8 (CAUA), the 4.2 FSI V8 runs two camshaft-driven high-pressure fuel pumps. The N276 fuel metering/pressure regulator solenoid integrated into the pump is a documented failure point, and the solenoid is not sold separately, so a failure condemns the whole pump. Separately, the steel cam follower (tappet) that rides between the camshaft lobe and the pump plunger wears through; if it is not replaced with the pump, it can destroy the new pump and score the camshaft lobe. Owners see fuel-pressure DTCs and hard starting or stalling. This is distinct from the electric in-tank low-pressure pump.

On the 2008-2017 Audi S5, the B8/B8.5 chassis uses a multi-link front end with four control arms per side (two upper, two lower) riding on small rubber bushings. The bushings crack and the ball joints develop play, producing a clunk or rattle over bumps (worst while turning) and a vague, wandering feel at highway speed, along with uneven inner tire wear. Surface cracking shows up as early as 30-40k miles; audible symptoms usually arrive between 70k and 100k. Because a failed ball joint changes camber and toe, this is a handling and tire-wear concern as well as a noise complaint. This is a chassis issue and applies across every B8 S5 drivetrain.

On the 2008-2017 Audi S5, b8 A5/S5 coupes route sunroof water down four drain tubes. The rubber elbow coupling where the tube meets the sunroof cassette hardens and stops sealing, and the tubes themselves clog with debris. Water then runs down the A-pillar and into the front footwell, or into the rear footwell from the back drains. Owners frequently misdiagnose it as a windshield or door seal leak, and it is often compounded by a separate clogged A/C evaporator drain that wets the passenger side. Left alone, standing water rots carpet and soaks control modules under the seats, which is how these cars end up with strange electrical faults.