The 2017 Audi S5 with the 3.0T supercharged V6 is generally reliable but shares critical weak points with the B8.5 platform, particularly catastrophic timing chain failures and transmission cooling issues that can lead to expensive repairs if neglected.
Timing Chain Tensioner Failure Leading to Engine Carnage
Occasional · high severityTypical onset: 80,000-140,000 mi
Symptoms: Cold-start rattle lasting 2-5 seconds that progressively worsens, Check engine light with timing correlation codes (P000A, P000B), Catastrophic failure: sudden loss of power, violent mechanical noise, no restart
Fix: If caught early with just rattle, timing chain service runs 12-16 hours labor. If tensioner fails completely, chain jumps timing and valves contact pistons—requires full engine rebuild or replacement. Early intervention is critical.
Estimated cost: $3,500-5,000 preventive service, $12,000-18,000 post-failure rebuild
Transmission Oil Cooler Line Leaks and Cooler Failure
Common · high severityTypical onset: 60,000-100,000 mi
Symptoms: Transmission fluid spots under vehicle, often pink/red, Harsh shifting or slipping when transmission overheats, Low transmission fluid warning on cluster, In severe cases, coolant mixing with ATF causing milky fluid
Fix: Factory cooler lines crack at crimp points; cooler itself can internally leak mixing coolant and ATF. Replace lines and cooler together (8-10 hours). If contamination occurred, full flush and possible valve body replacement needed.
Estimated cost: $1,800-3,200 for lines/cooler, $4,000-6,500 if contamination damage
Carbon Buildup on Intake Valves
Common · medium severityTypical onset: 50,000-80,000 mi
Symptoms: Rough idle and misfires at cold start, Loss of power and throttle response, especially under 3,000 RPM, Increased fuel consumption, Multiple cylinder misfire codes (P0300-P0306)
Fix: Direct injection engines with no port injection suffer heavy valve carbon deposits. Requires walnut blasting media cleaning—supercharger removal for access adds complexity. 6-8 hours labor. Should be done every 50-60k miles as preventive maintenance.
Estimated cost: $800-1,400
Transmission Mounts Deteriorating
Common · low severityTypical onset: 70,000-110,000 mi
Symptoms: Clunking when shifting from Park to Drive or Reverse, Vibration through chassis at idle in Drive, Excessive drivetrain movement visible during acceleration, Transmission appears to sag when inspected on lift
Fix: Hydraulic transmission mounts fail from age and stress. Front mount most common, but recommend replacing all mounts simultaneously. 3-4 hours labor with subframe support required.
Estimated cost: $600-1,100
Water Pump and Thermostat Housing Leaks
Occasional · medium severityTypical onset: 80,000-120,000 mi
Symptoms: Coolant smell in cabin or under hood, Visible coolant weeping from front of engine, Low coolant warning light, Overheating in severe cases if leak progresses
Fix: Plastic thermostat housing and water pump develop leaks at gasket surfaces or crack from heat cycles. Replace both together with updated parts—10-12 hours with supercharger removal for proper access. Don't chase individual leaks.
Estimated cost: $1,800-2,800
PCV System and Valve Cover Gasket Oil Leaks
Common · low severityTypical onset: 60,000-100,000 mi
Symptoms: Oil residue on top of engine and around valve covers, Burning oil smell from exhaust heat, Oil consumption between changes (1 qt per 2,000-3,000 mi), Check engine light for intake system leaks (P2279, P2261)
Fix: Valve cover gaskets shrink and PCV diaphragms tear, causing vacuum leaks and oil seepage. Replace gaskets, PCV valve, and pressure regulation valve. 4-5 hours labor. Often done during carbon cleaning.
Estimated cost: $800-1,300
Buy one with documented timing chain service under 100k miles and verified clean transmission history; otherwise budget $5k+ immediately for deferred maintenance—the drivetrain grenades when neglected.
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.