The B7 S4's 4.2L V8 is a brilliant motor when healthy, but the timing chain guides and carbon buildup are ticking time bombs. These cars reward meticulous maintenance but punish neglect with catastrophic engine failure.
Timing Chain Guide Failure
Common · high severity
Typical onset: 60,000-120,000 mi
Symptoms: Cold-start rattle for 2-3 seconds that worsens over time, Check engine light with timing correlation codes, Metallic rattling from front of engine, Catastrophic engine failure if guides disintegrate
Fix: Engine-out job requiring complete timing service including guides, tensioners, chains, and cam adjusters. 20-25 labor hours. This is THE failure point on this platform—guides are plastic and wear predictably. Many techs recommend doing it preventively at 80k if history is unknown.
Estimated cost: $4,500-7,000
Carbon Buildup on Intake Valves
Common · medium severity
Typical onset: 40,000-80,000 mi
Symptoms: Rough idle and misfires, Loss of power and throttle response, Increased fuel consumption, P0300-series misfire codes
Fix: Direct-injection engines with no fuel washing the valves. Walnut blasting is the gold standard—media blasting each runner with engine partially disassembled. 6-8 hours labor. Catch-can systems help prevent recurrence but don't fix existing buildup.
Estimated cost: $800-1,400
Transmission Oil Cooler and Thermostat Failure
Common · medium severity
Typical onset: 80,000-130,000 mi
Symptoms: Harsh shifts when cold, Delayed engagement into gear, Transmission slipping or banging into gear, Milky transmission fluid if cooler fails internally
Fix: The external cooler and thermostat fail, causing poor fluid temps and accelerated clutch wear in the 6-speed auto. Replace both as a set with fresh fluid. 3-4 hours. If coolant mixes with ATF from internal leak, you're looking at a full transmission rebuild.
Estimated cost: $600-1,200
Control Arm Bushings and Ball Joints
Common · medium severity
Typical onset: 60,000-100,000 mi
Symptoms: Clunking over bumps, Wandering steering and poor alignment retention, Uneven tire wear, Vibration under braking
Fix: Audi's pressed-in bushings fail regularly. Front lower control arms typically need replacing as assemblies (bushings aren't serviceable separately on most). Budget 4-6 hours for a full front refresh including both lowers, uppers, and links.
Estimated cost: $1,200-2,000
Secondary Air Injection Pump Failure
Occasional · low severity
Typical onset: 70,000-120,000 mi
Symptoms: Check engine light on cold start with P0411 or P0491, Loud buzzing or grinding noise for 60 seconds after cold start, Emissions test failure in states that check readiness monitors
Fix: Pump motor or check valves fail. Not critical to drivability but triggers CEL and emissions issues. Pump replacement is 2-3 hours. Some owners delete the system entirely in non-emissions states, but that requires tuning.
Estimated cost: $600-1,000
Oil Consumption and Piston Ring Failure
Occasional · high severity
Typical onset: 80,000-150,000 mi
Symptoms: Burning 1+ quart every 1,000 miles, Blue smoke on deceleration or startup, Fouled spark plugs, Loss of compression on certain cylinders
Fix: Rings can stick or wear, especially on neglected oil change intervals. Minor consumption (1qt/2k mi) is manageable with monitoring. Severe cases need engine-out rebuild with new pistons and rings. 30+ hours labor. Some opt for used engine swaps instead.
Estimated cost: $8,000-12,000
Thermostat and Coolant Flange Leaks
Common · low severity
Typical onset: 60,000-100,000 mi
Symptoms: Coolant seepage at thermostat housing, Low coolant warning light, Erratic temperature gauge readings, Sweet coolant smell in cabin or under hood
Fix: Plastic thermostat housing and rear coolant flanges crack over time. Thermostat replacement is 2-3 hours; rear flanges require more disassembly (4-5 hours). Use updated metal parts where available.
Estimated cost: $400-900
Owner tips
Check timing chain guides via borescope before buying—this is non-negotiable on high-mileage examples
Walnut blast the intake valves every 40-50k miles and consider a catch-can system to slow carbon accumulation
Change transmission fluid every 40k miles regardless of 'lifetime fill' claims—it extends auto trans life significantly
Always use 5W-40 full synthetic and change every 5k miles maximum to prevent ring sticking and sludge
Budget $2k/year in maintenance and repairs if buying over 80k miles—these are not cheap to own
Buy one only if timing chains are documented done or you budget for them immediately—otherwise you're gambling with a $6k repair, but they're fantastic drivers when sorted.
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.
Fitment notes: Battery located in trunk on passenger side; requires AGM for proper vehicle electronics operation; high CCA requirement for 4.2L V8
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Every control module on the 2004-2007 Audi S4 — where it lives, replacement time, and what it takes to program a replacement. Modules marked dealer / factory tool won't work after a part swap alone — budget for programming.
📍 Integrated into ABS module or separate module in trunk
🔧 VCDS
⚠️ Optional; indirect TPMS using ABS wheel speed sensors; relearn procedure after tire rotation
Aftermarket tool coverage varies by software version and vehicle build — treat "aftermarket tool" rows as "usually possible" and verify against your tool maker's coverage list before promising a customer. Spot a wrong location or hour? Tell us — corrections ship fast here.
AIR BAGS:FRONTAL:PASSENGER SIDE:INFLATOR MODULE · 18V427000
2018-06-22 · EA15001
Volkswagen Group of America, Inc. (Volkswagen) is recalling certain 2005-2008 Audi A4 Sedan, A4 Avant, S4 Avant and S4 Sedan, 2007-2008 RS4 Sedan, 2004 RS4 Cabriolet, 2007-2009 A4 Cabriolet and S4 Cabriolet, 2005-2011 A6 Sedan, 2006-2011 A6 Avant, and 2007-2011 S6 Sedan vehicles. These vehicles are equipped with certain air bag inflators assembled as part of the passenger frontal air bag modules used as original equipment or replacement equipment. In the event of a crash necessitating deployment of the passenger frontal air bag, these inflators may explode due to propellant degradation occurring after long-term exposure to absolute humidity and temperature cycling.
Consequence: An inflator explosion may result in sharp metal fragments striking the driver or other occupants resulting in serious injury or death.
Remedy: Audi has notified owners, and dealers will replace the passenger frontal air bag with an alternate remedy part, free of charge. The recall began June 29, 2018. Owners may contact Audi customer service at 1-800-253-2834. Volkswagen's number for this recall is 69R7. Note: This recall supersedes recalls 16V382, 17V032 and 18V004 and includes vehicles that may have had their air bag previously replaced under one of those campaigns.
AIR BAGS:FRONTAL:PASSENGER SIDE:INFLATOR MODULE · 17V032000
2017-01-11 · EA15001
Volkswagen Group of America, Inc. (Volkswagen) is recalling certain 2009 Audi A4 Cabriolet, S4 Cabriolet, A6 Avant, A6 Sedan and S6 Sedan vehicles originally sold, or ever registered, in Arizona, Arkansas, Delaware, the District of Columbia, Illinois, Indiana, Kansas, Kentucky, Maryland, Missouri, Nebraska, Nevada, New Jersey, New Mexico, North Carolina, Ohio, Oklahoma, Pennsylvania, Tennessee, Virginia, and West Virginia, or "Zone B."
Additionally, unless included in "Zone B" above, Volkswagen is recalling certain 2005-2008 Audi A4 Avant, A4 Sedan, A6 Sedan, S4 Avant and S4 Sedan vehicles, 2007-2008 A4 Cabriolet, RS4 Sedan, S4 Cabriolet and S6 Sedan vehicles, and 2006-2008 A6 Avant and 2008 RS4 Cabriolet vehicles originally sold, or ever registered, in Alaska, Colorado, Connecticut, Idaho, Iowa, Maine, Massachusetts, Michigan, Minnesota, Montana, New Hampshire, New York, North Dakota, Oregon, Rhode Island, South Dakota, Utah, Vermont, Washington, Wisconsin, and Wyoming.
These vehicles are equipped with certain air bag inflators assembled as part of the passenger frontal air bag modules used as original equipment or replacement equipment. In the event of a crash necessitating deployment of the front air bags, these inflators may rupture due to propellant degradation occurring after long-term exposure to absolute humidity and temperature cycling.
Consequence: An inflator rupture may result in metal fragments striking the vehicle occupants resulting in serious injury or death.
Remedy: Audi will notify owners, and dealers will replace the passenger frontal air bag inflator, free of charge. The recall began March 30, 2018. Owners may contact Audi customer service at 1-800-253-2834. Note: This recall has been superseded by recall number 18V427.
Performance
Horsepower
340hp
Torque
302lb-ft
0–60 mph
4.9sec
Quarter mile
13.4sec
Top speed
155mph
Fuel economy (EPA)
City
14mpg
Highway
20mpg
Combined
16mpg
Fuel
Premium Gasoline
Capability & size
Curb weight
4,045lb
EPA class
Subcompact Cars
Wiper blades
B7 generation sedan. Some sources show 22/19 configuration.
Size-standard part numbers — verify your connector type before buying. Rear blades are model-specific; check the package's vehicle list.
Fuel economy figures are EPA data via fueleconomy.gov (median across matching trims). Performance figures are compiled estimates for the 2005–2008 Audi S4 4.2L V8 and can vary by trim.
🔧 Database maintained under the daily editorial review of Chris Hackleman · Master Technician · 20+ years.