A compelling performance daily driver with Audi's advanced twin-turbo V6. The 2.9 TFSI EA839 is shared with Porsche and generally reliable when maintained properly. Main concerns center on the water pump (known weak point causing cascading failures), PCV valve membrane failures, early production rocker arm issues (resolved after August 2018), and control arm bushings wearing around 60,000-80,000 km. The S-Tronic dual-clutch is robust but requires strict 35k/40k service intervals. Carbon buildup is less severe than older generations but walnut blasting still recommended every 50,000-60,000 km. Overall one of the more reliable high-performance Audis, provided you stay on top of preventive maintenance.
Water pump / coolant control valve failure€1,200 - €4,500
Design flaw causes coolant leak into vacuum system, typically fails before 80,000 km · more· less
The EA839 engine has an inherent flaw in the mechanical design of the factory water pump. When it fails (not if, but when), coolant can migrate into the vacuum system, damaging the vacuum pump and potentially the brake servo if left unaddressed. Most failures occur under 50,000 miles (80,000 km). Audi has developed an updated water pump design. Dealer quotes range from €1,200-1,500 for just the pump, but can reach €4,000-5,400 if the vacuum pump, coolant bypass valve, and vacuum solenoid also need replacement due to coolant contamination. Independent specialists charge around €2,500-3,500 for the comprehensive repair. Watch for dried coolant residue on the front of the engine.
Membrane tears causing pressure buildup, can blow oil cap off and damage rear main seal · more· less
The PCV valve has a membrane that can tear, causing back pressure in the crankcase. This pressure can blow the oil filler cap off, spewing oil throughout the engine bay. In severe cases, pressure finds the next weak point—typically the rear main seal. Symptoms include rough idle, oil consumption, oil leaks, and check engine light. Most failures occur between 60,000-100,000 km. Audi extended the warranty on PCV systems to 7-8 years due to this known issue. The genuine Audi PCV valve costs €400-600. Aftermarket upgrades like 034 Motorsport's billet PCV system (€270 DIY) are available. Replacing just the PCV at an independent shop runs €500-900 including labor.
Control arm bushings wear€600 - €1,800
Front upper bushings crack and become brittle, typically 60,000-100,000 km · more· less
Control arm bushings are a known weak spot on performance Audis. The bushing material cracks and becomes brittle over time, particularly on heavier S/RS models. Failures typically occur around 50,000-65,000 miles (80,000-100,000 km) and are more time/age-related than mileage-dependent. Symptoms include clunking over bumps and imprecise steering. Most shops recommend replacing the entire control arm rather than just pressing in new bushings, as the ball joints should also be replaced and it's more cost-effective. Parts cost around €200-400 per arm. Labor is 3-4 hours per side. Dealer quotes reach €1,500-1,800 for both front uppers; independent shops charge €600-1,200. Aftermarket upgraded arms like 034 Motorsport's density line are popular.
Rocker arm failure (2017-2018 models only)€2,500 - €6,000
Early production needle bearings too small, can cause cam sensor ring displacement · more· less
The original rocker arms (part 06M109417H, used until 11.09.2017) had undersized needle roller bearings that could slip out of the bearing race. The first revision (06M109417L, 11.09.2017 to 06.08.2018) improved but didn't fully solve the issue. The final revised version (0P2109417, from 06.08.2018 onwards) uses much larger bearings and is considered resolved. Most EA839 engines after August 2018 don't have this problem. Symptoms include constant ticking noise or, if broken, multiple misfires and rough running. Replacement requires removing camshafts and involves all 24 rocker arms. Professional installation strongly recommended. Costs range from €2,500-6,000 depending on additional damage. Check production date—2019+ models are safe.
Wastegate lever can fracture from fatigue, water pump failure damages vacuum system · more· less
Two separate but related issues: (1) The turbo wastegate lever can break due to fatigue—documented failures at 96,000 km show the lever is "wimpy and not up to the task." (2) When the water pump rod seals fail, coolant enters the vacuum pump and gets ingested, failing the vacuum system. Without proper vacuum, the wastegate actuator can't function, triggering P0299 (Turbo Underboost) codes and limp mode. Early 2017-2018 RS5s had a wastegate software issue addressed by TSB 2052094/3 (September 2019). Late-built 2019+ should have no issues. Repair costs depend on whether it's just the actuator, wastegate components, or if water pump damage caused collateral turbo damage. Twin turbos make this expensive: €1,500-2,500 for actuators, €3,000-4,500+ if turbo replacement needed.
Carbon buildup on intake valves€600 - €1,400
Direct injection causes deposits, walnut blasting recommended every 50,000-60,000 km · more· less
The 2.9 TFSI uses direct injection only (no port injection), making it susceptible to carbon buildup on intake valves. Good news: B9 RS5 owners report carbon buildup is much less severe than earlier generations due to design improvements. Still, buildup gradually restricts airflow, causing rough idle, misfires, and reduced performance. Walnut blasting (media blasting) is the most effective cleaning method. Independent specialists charge €600-900; dealers €1,000-1,500. The process takes 4-6 hours for manifold removal/reinstallation plus 30 minutes per cylinder (about 10 hours labor total). Recommended interval: 30,000-40,000 miles (50,000-65,000 km). Chemical treatments like Forte Power Clean every 15,000-25,000 km can slow buildup between proper cleanings.
DSG S-Tronic mechatronic unit issues€2,000 - €5,000
Harsh shifts or hesitation when cold, mechatronic PCB/solenoid failures if service neglected · more· less
The DL-501 S-Tronic transmission in the B9 RS5 is generally reliable but sensitive to maintenance intervals. Early B9 S4s reported harsh shifts and mechatronic control unit problems, addressed via software updates. Common complaints include rough 2-1 downshifts when cold, mid-turn downshift jerking, and hesitation after canceling cruise control. The mechatronic unit contains PCB, solenoids, and thermostats that wear over time—failures occur when ATF service intervals are stretched beyond 40,000 km. Proper service schedule: first change at 35k miles (56,000 km), then every 40k miles (64,000 km). Each service should include ATF fluid, external filter, and internal strainer. Service costs €400-850 at specialists; £550-840 at dealers. Neglecting this leads to mechatronic failures costing €2,000-5,000 for repair or replacement.
Timing chain tensioner rattle€2,500 - €3,700
Tensioner loses pressure overnight, causes 1-30 second cold start rattle · more· less
The EA839 uses timing chains (no belt to replace). The tensioner has a release valve that can weaken over time, allowing oil pressure to bleed off overnight. This results in a distinctive rattle for 1-30 seconds on cold start until oil pressure builds. If rattle lasts more than a few seconds or occurs regularly, the chain, guides, tensioners, and sprockets all need replacing. Audi TSB 15 15 26 addresses startup noise with improved tensioners. Using VCDS you can check for chain stretch. Typical timing chain replacement costs €2,500-3,000 at independent shops, €3,000-3,700 at dealers. This is complicated work requiring precise timing—mistakes cause severe engine damage. Not a DIY job. The 2.9 TFSI is generally better than older VAG engines for this issue, but still monitor for cold start noise.
Fuel injector failure€700 - €1,800
Direct injection injectors clog or fail, causing misfires and rough idle after 80,000-100,000 km · more· less
Fuel injectors in direct injection engines like the 2.9 TFSI can clog or fail, typically after 80,000-100,000 km. Symptoms include rough idle, hard starting, strong fuel smell, misfires (P0300, P0303 codes), and potential hydrolocking if injector sticks open. VCDS diagnostics reveal elevated misfire counts. A stuck-open injector will have a wet spark plug and contaminate engine oil with gasoline—if this happens, change oil immediately. Injectors must be replaced as a set (all 8) with new seals. Genuine Audi/VW injectors cost €80-100 each; Bosch equivalents (same part, no VW logo) cost €40-50 each. Dealer charges €1,200-1,800 for the job. Independent shops or DIY with aftermarket parts: €700-1,100. Requires intake manifold removal—8-10 hour job.
Rear sport differential service / failure€400 - €5,000
Fluid service required every 56,000 km; neglect causes expensive differential replacement · more· less
The RS5's rear sport differential requires ATF fluid and differential oil changes. First service at 35,000 miles (56,000 km) or 3.5 years, then every 40,000 miles (64,000 km). Fluid change for all three differentials (front, center, rear) costs €400-600. The middle diff fluid alone is ~€100/liter due to special viscosity—must buy from Audi. Symptoms of failure include high-pitched whine under acceleration (disappears when coasting), or "sport diff malfunction" warning. Failures are rare but expensive: differential replacement costs around €5,000. Actuator/sensor failures cost £600 (€700) for parts and labor. Regular fluid service is cheap insurance—€150 service vs €5,000 replacement. Track use accelerates wear; consider 40,000 km intervals if driven hard.
Virtual cockpit settings not saving, CarPlay blackouts, display cycling on startup · more· less
Common MMI issues include: (1) Virtual cockpit settings not saving when switching to RS mode—fix requires turning off "automatic RS layout" slider in settings. (2) CarPlay going black, requiring clicking in/out to restore. (3) Virtual cockpit display glitching/cycling for 1-2 minutes on startup, particularly on 2020 models. Software updates sometimes resolve issues, but some cases require instrument cluster replacement (€1,200-1,500, must order from Germany). Check for loose cables/connections behind dashboard and ensure firmware is current. USB ports can be damaged by debris. These issues are annoying but not safety-critical. Extended warranty may cover instrument cluster replacement. "These cars run a lot of code"—expect occasional software quirks.
Generally reliable for a high-performance car, but maintenance is expensive
The B9 RS5's 2.9 TFSI is one of Audi's more reliable performance engines, shared with Porsche. Owners report surprisingly few drivetrain failures despite the complex twin-turbo setup. However, when issues occur, repair costs are high due to mid-engine packaging and premium parts pricing. The water pump is the Achilles heel—budget for preemptive replacement. Stay religious with DSG service intervals and oil changes every 8,000 km (not 15,000 km). Models built after August 2018 avoid early rocker arm problems. With proper preventive maintenance, these cars easily exceed 200,000 km.
Pre-Purchase Inspection Checklist
General checks
Service history
Complete Audi dealer or specialist records essential. Verify oil changes at 8,000-10,000 km intervals (not 15,000 km), DSG service every 40,000 km, and rear diff service every 56,000 km.
Tires
Stock sizes: 265/35R19 or 275/30R20. Check tread depth (minimum 3mm), age (date codes—replace after 6 years), and uneven wear. Premium tires (Michelin PS4S, Pirelli P Zero) cost €350-450 each.
Cold start
Must start engine completely cold. Listen carefully for timing chain rattle in first 30 seconds. Slight rattle for 1-2 seconds can be normal; anything longer indicates tensioner/chain wear.
Body condition
Check for accident damage, paint mismatch, water stains in footwells (indicates sunroof drain blockage). Inspect undercarriage for scrapes.
Test drive
Minimum 30 minutes including highway speeds. DSG needs to warm up to reveal issues. Test hard acceleration, downshifts, and RS mode.
Specific for this vehicle
Check production date and rocker arm revision
Build date after August 2018 = revised rocker arms (safe). 2017-2018 models should have rocker arms inspected or documented replacement with part 0P2109417.
Inspect water pump area for coolant residue
Look at front of engine for dried coolant stains or dampness. Check coolant reservoir level—if low, pump may be leaking. This is the most common expensive failure on EA839.
Check for PCV valve failure symptoms
Look for oil residue around engine bay, particularly near oil filler cap. Check if oil cap is loose or aftermarket (indicates previous PCV blowout). Test for rough idle.
Verify DSG service history
First service should be at 35,000 miles (56,000 km), then every 40,000 miles. Confirm both ATF and MTF fluids were changed. Missing records = walk away or budget for immediate service.
Test virtual cockpit and MMI extensively
Cycle through all display modes, check if settings save. Test CarPlay/Android Auto. Look for screen glitching during startup. These issues are common but fixable.
Inspect control arm bushings
Jack up front and check for play in upper control arms. Look for torn/cracked rubber bushings. Common failure point at 60,000-100,000 km.
Run VCDS diagnostics if possible
Check for hidden fault codes, misfire counts, timing chain stretch values, and adaptation data. Ross-Tech VCDS cable costs €199—invaluable for Audi ownership.
Check for recall/TSB completion
Verify wastegate TSB 2052094/3 applied (2017-2018 models). Check PCV extended warranty status. Contact Audi with VIN to confirm all recalls complete.
Check carbon ceramic brakes thoroughly (if equipped)
Measure AND weigh discs—visual inspection insufficient at high mileage. CCB rotors cost €5,000+ each; budget iron rotor conversion (€1,450 complete kit) if worn.
Listen for rear differential whine
High-pitched whine under acceleration (disappears when coasting) indicates differential wear. Verify fluid service history—neglect causes €5,000 failure.
Contact Audi with VIN to verify all recalls and TSBs completed. Check for Software Version Management (SVM) updates—Audi frequently releases software improvements for drivetrain and MMI systems.
Warranty Status
Factory warranty (2 years)Expired on 2017-2022 models
Powertrain warranty (3 years)Expired on 2017-2021 models
PCV extended warranty7-8 years (check eligibility)
Audi extended warrantyAvailable, €1,500-2,500/year
Extended warranty may be worthwhile given high repair costs, but read exclusions carefully. Water pump coolant leaks, oil leaks, and wear items (bushings, brakes) typically not covered. Best value: buy from low-mileage owner with remaining factory warranty, then maintain meticulously yourself.
This report is for informational purposes only and does not constitute professional advice. Estimates may be inaccurate. Always have a qualified specialist inspect the vehicle before purchase. We accept no liability for decisions made based on this information.