Audi S4: common faults & what to check

Which Audi S4 are you looking at?

3 generation variants documented. Pick the shape you recognise: the faults, the servicing and the timeline below all narrow to it. Free, no account needed.

Engine not documented

3 variants documented

2001–2008B62001–2008B6Engine not documented for this generationEngine not documentedDocumented issues2 knownSee faults & what to checkPhoto: MercurySable99 via Wikimedia Commons, CC BY-SA 4.0.

2008–2016B82008–2016B8Engine not documented for this generationEngine not documentedDocumented issues7 knownSee faults & what to checkPhoto: Shawn Jooste via Wikimedia Commons, CC BY 2.0.

2016–nowB92016–nowB9Engine not documented for this generationEngine not documentedDocumented issues1 knownSee faults & what to checkKickTyres illustration, not a photograph.

Now narrow it to the engine

A 1.8 and a 2.4 of the same car do not fail the same way, so the faults below narrow to the engine as well as the year. Free, no account needed.

Start your free check on this Audi S4

No plate needed. You get the risk score, the buyer's checklist and the guided inspection for the exact car you picked above — not the whole nameplate.

The checks worth doing on a Audi S4 before you hand over any money. Every documented fault is listed below, each with its own page.

• Serious issue

  Test drive in slow stop-start traffic and note any shuddering when pulling away from rest.

  See why

  S tronic DL501 mechatronic unit failure (B8 S4 7-speed S tronic)

  The 7-speed S-tronic dual-clutch transmission (DL501 / 0B5 code) used longitudinally in the A4 pairs a wet multi-plate clutch pack with an electro-hydraulic mechatronic control unit. The mechatronic valve body develops internal hydraulic leaks and solenoid faults causing shuddering at low speed, harsh or refused gear engagement, and in severe cases complete loss of drive. Clutch pack wear also produces juddering when pulling away from rest. Audi extended the warranty in some markets but units outside warranty require full replacement. B9 variants retained DL501 and share the same failure mode.

  What you would notice

  • Shuddering or vibration when pulling away at low speed
  • Harsh, jerky downshifts especially in traffic
  • Transmission warning light or failsafe mode
  • Delayed or refused engagement from Park or Neutral

  Typically $3,000–$8,000 to put right.

• Serious issue

  Look at both rear tyres for uneven wear across the tread, especially the inner edges.

  See why

  B9 S4 rear axle nuts may break on some 2019-2021 cars, recall REC-001665 (check VIN)

  On some 2019 to 2021 B9 Audi S4s (and other A4, A5 and larger Audis of those years) nuts fitted to the rear axle did not meet specification and can break, letting the rear wishbone move against the hub carrier and suddenly changing the rear wheel alignment. Audi Australia recalled 1,622 cars in September 2021 (REC-001665, campaign 42L1) to replace the nuts free of charge. A follow-up recall in March 2022 (REC-005076, campaign 42L5) corrects rear misalignment and tyre wear caused by some of the first repairs. 2017 and 2018 cars are not part of this recall. Only cars listed by VIN are affected.

  What you would notice

  • Clunk from the rear over bumps
  • Car pulls or the rear feels unsettled
  • Uneven or fast wear on the inner edges of the rear tyres

  Typically $0–$600 to put right.

• Costly issue

  Inspect the front control arm bushes visually for splitting, tearing, or separation of the rubber from the steel insert.

  See why

  Front Lower Control Arm Ball Joint and Bush Wear

  The front suspension on B6, B7, and B8 A4 models uses aluminium lower control arms (wishbones) with pressed-in rubber-bonded bushes and an integral ball joint at the outboard end. Both the front bush and the ball joint wear faster than expected on these arms, particularly on vehicles used in urban driving with frequent low-speed cornering and kerbing. On OEM control arms, the ball joint cannot be replaced separately — once the ball joint wears beyond limits, the entire control arm must be replaced. The front bush deteriorates under load cycling and can allow the arm to move fore-aft, degrading steering response and causing tyre wear. Worn ball joints, if left uncorrected, eventually develop enough play to separate under load, causing sudden loss of front-wheel steering geometry control.

  What you would notice

  • Clunking or knocking from the front suspension when driving over potholes, speed bumps, or rough road surfaces
  • Vague or imprecise steering, particularly on initial turn-in, caused by front bush deflection under load
  • Uneven tyre wear across the front axle, often showing greater wear on the inner or outer shoulder
  • Steering pulling to one side under hard braking, suggesting one side is worn more than the other

  Typically $550–$1,900 to put right.

• Costly issue

  Inspect the valve cover oil separator housing for cracks and check the large vacuum hose from valve cover to intake for oil contamination.

  See why

  PCV / Oil Separator Valve Failure

  The EA888 positive crankcase ventilation (PCV) system incorporates an oil separator integrated into the valve cover. The membrane diaphragm and check valves crack with age and heat cycling. A failed PCV draws oil vapour directly into the intake manifold, fouling the throttle body and intake valves with carbon deposits on direct-injection engines, and causes excessive oil consumption through the intake tract. Intake valve carbon build-up reduces airflow and causes misfires. Gen 3 engines (CYMC, B9) retained this vulnerability.

  What you would notice

  • Blue-grey smoke from exhaust under deceleration
  • Oil level dropping between services with no visible external leak
  • Hissing or sucking noise from valve cover area
  • Rough idle and misfires after extended use

  Typically $400–$1,200 to put right.

• Costly issue

  During a test drive, note whether the rear of the car tramlines, wanders, or feels unsettled over undulations and during braking from speed.

  See why

  Rear Subframe Bush Deterioration

  The B6, B7, and B8 A4 rear subframe is located and compliant-mounted to the body via large rubber bushes at four mounting points. These bushes carry significant longitudinal and lateral loads from the rear suspension and are subject to long-term rubber degradation from ozone, heat, and fatigue. As the bushes deteriorate, the subframe develops controlled but unintended movement under braking and acceleration loads. This directly affects rear wheel alignment — particularly toe angle — causing the rear wheels to steer slightly as the subframe shifts, producing instability and tyre scrub. The condition is often missed at standard service inspections but can be confirmed by physically inspecting or applying load to the subframe during a workshop check.

  What you would notice

  • Rear-end instability or wandering during motorway driving, requiring constant minor steering corrections
  • Clunking or thudding from the rear of the car during hard braking or sharp acceleration
  • Uneven rear tyre wear, typically feathering or diagonal wear on the inner edge from dynamic toe changes
  • Loose or imprecise steering feel that worsens at higher speeds

  Typically $700–$2,000 to put right.

• Costly issue

  After a test drive of at least 15 minutes, check the coolant temperature gauge behaviour throughout the drive and after shutdown.

  See why

  Electric auxiliary coolant pump failure — overheating

  The B9 A4 2.0 TFSI uses an electric auxiliary coolant pump (EWP) to circulate coolant through the turbocharger and heater core when the main belt-driven pump cannot maintain adequate flow, and to provide post-run cooling after engine shutdown. These electric pumps are known to fail due to impeller wear or motor burnout, particularly on vehicles above 80,000 km. Failure triggers a coolant temperature warning and can cause the engine to overheat if ignored. The turbocharger may also suffer heat-soak and bearing damage after engine shutdown if the post-run circulation pump has failed silently.

  What you would notice

  • Coolant temperature warning light or gauge reading higher than normal operating range
  • Reduced heater output with cold or intermittent air from cabin vents
  • Fault codes for auxiliary coolant pump circuit open or short (P260D or manufacturer-specific code)
  • Overheating warning during or shortly after sustained high-speed or hard driving
  • Absence of the normal electric pump whirring sound from the engine bay during post-shutdown cooling cycle

  Typically $600–$1,800 to put right.

Audi S4 service schedule

What falls due, and at what distance, for each generation of the Audi S4. These are the model’s intervals — the car’s own service book is the only thing that can tell you what has actually been done to it.

What these repairs cost on other cars

Some of the Audi S4’s documented faults are repairs other models share. Each page lists the documented NZ cost for every model it affects.

• DSG and Dual-Clutch Gearbox Repair Cost

Other Audi models