The 2011 Audi S5 with the 4.2L V8 is a high-strung performance coupe that rewards meticulous maintenance but punishes neglect with catastrophic engine failures. The naturally-aspirated FSI engine is notorious for carbon buildup and oil consumption that can lead to piston ring failure and full engine rebuilds if not addressed early.
Excessive Oil Consumption Leading to Piston Ring Failure
Common · high severityTypical onset: 60,000-100,000 mi
Symptoms: Burning more than 1 quart per 1,000 miles, Blue smoke on startup or under load, Low oil pressure warning, Misfires on multiple cylinders, Carbon deposits visible in intake ports
Fix: Audi extended warranty covered some cases, but post-warranty you're looking at engine-out piston ring replacement or full short-block replacement. Rings alone: 30-40 labor hours. Full short block: 35-45 hours including fluids and timing chain service while it's apart.
Estimated cost: $8,000-15,000
Carbon Buildup on Intake Valves (Direct Injection Issue)
Common · medium severityTypical onset: 40,000-80,000 mi
Symptoms: Rough idle, Hesitation or stumble on acceleration, Misfires (P0300-P0308 codes), Reduced fuel economy, Failed emissions test
Fix: Direct injection means no fuel washing over valves. Walnut blasting the intake ports is the proper fix—requires removing intake manifold. Takes 4-6 hours for a V8. Preventive every 50k miles is wise on these engines.
Estimated cost: $600-1,200
Transmission Oil Cooler Lines Leaking
Occasional · medium severityTypical onset: 70,000-120,000 mi
Symptoms: Transmission fluid spots under car, Burnt transmission fluid smell, Erratic shifting or slipping when fluid is low, Fluid visible on subframe or underbody
Fix: The cooler lines corrode where they connect to the radiator or at crimp points. Replacement involves dropping the subframe or working from below with the car on a lift. 3-4 hours labor plus fluid refill and adaptation with VCDS.
Estimated cost: $800-1,400
Transmission Mounts Collapsing
Occasional · medium severityTypical onset: 60,000-100,000 mi
Symptoms: Clunk when shifting from Park to Drive or Reverse, Vibration at idle in gear, Excessive driveline movement under hard acceleration, Visible sagging or torn rubber on mount inspection
Fix: The rear transmission mount takes a beating on these torquey cars. Replacement requires supporting the transmission and unbolting the crossmember. 2-3 hours. Often done alongside motor mounts if those are also worn.
Estimated cost: $400-700
Timing Chain Tensioner and Guide Wear
Occasional · high severityTypical onset: 80,000-130,000 mi
Symptoms: Rattling on cold start for first 2-3 seconds, Metallic ticking from front of engine, Check engine light with cam/crank correlation codes (P0016, P0017), Metal shavings in oil filter
Fix: The 4.2L FSI uses multiple chains and tensioners. If they fail, you get valve-to-piston contact. Preventive replacement at 100k is smart. Engine-out not required but front of engine must be disassembled. 12-18 hours labor depending on how far you go (chains only vs full guides and rails).
Estimated cost: $3,000-5,500
Fuel Injector O-Ring Leaks and Injector Failures
Occasional · medium severityTypical onset: 80,000-120,000 mi
Symptoms: Fuel smell in cabin or engine bay, Rough idle and misfires, Fuel trims way out of spec (scan data), Visible fuel seepage at injector seals, Hard starting when hot
Fix: High-pressure direct injectors can leak at the seals or fail internally. Injectors are expensive ($200-400 each), and you need special tools to remove them without damaging the cylinder head. Figure 1 hour per injector for R&R, plus recalibration. Often do all 8 at once to avoid comeback.
Estimated cost: $2,500-4,500
Only buy if you have comprehensive service records proving religious oil changes and carbon cleaning, or budget $10k-15k for an eventual engine rebuild—this is a money pit without maintenance history.
AI-assisted summary drawn from NHTSA recall data, our labor-times database, and platform knowledge. Not a substitute for a pre-purchase inspection on a specific vehicle.