Reliability guide for used Audi A4, S4 and RS4 B9 cars
Produced between 2015 and 2023, the Audi A4 B9 is the fifth generation of the premium family sedan, available as a sedan, Avant (estate), and Allroad. The sporty S4 (supercharged 3.0 TFSI V6) and RS4 (twin-turbo 2.9 TFSI V6) versions offer a distinctly sporty character, while also benefiting from significant technological advancements compared to the B8.
Overall, the A4 B9 is more reliable than the previous generation , but some engines and technical elements deserve attention when buying.
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Highlights of the A4 B9
- The quality of the finish has improved significantly: modern interior, premium materials.
- Excellent comfort and soundproofing, especially in the high-end finish.
- Wide range of petrol and diesel engines, with mild hybrid (MHEV) versions.
- Dynamic road handling, especially in quattro.
- High-performance and modern S4 and RS4 sports versions.
Reliability by engine
Essence
1.4 TFSI (150 hp)
- Overall reliable and economical.
- Key points:
- Water pump/thermostat : frequent fluid leaks around 100,000 km.
- Ignition coils that can fail prematurely.
- Turbocharger : few reported cases, but expensive replacement in case of seizure.
- Well suited for short rides, but lacks power on the road.
2.0 TFSI (190-245 hp)
- A versatile, high-performance and fuel-efficient engine.
- Recurring flaws:
- Fragile water pump → coolant loss (bill between €500 and €900).
- Thermostat that remains open → engine that struggles to heat up.
- Oil consumption : rare but still reported on some examples <2018.
- High-pressure injectors sensitive to fouling → to be monitored in case of difficult starts.
- Significantly improved reliability after 2017 thanks to improvements in injection and segmentation.
Audi S4 B9 – 3.0 TFSI V6 (354 hp)
- Excellent compromise between performance and reliability, but not without weaknesses:
- Water pump and thermostat : frequent failures around 80-100,000 km.
- Chain tensioners : rattling when cold → risk of elongation if not treated.
- Fuel pressure sensor sometimes faulty → loss of power.
- Coils and spark plugs are sensitive if driven sportily repeatedly.
- Moderate oil consumption (1L/5000 km) sometimes observed.
- With proper maintenance, it's a reliable and enjoyable engine.
Audi RS4 B9 – 2.9 TFSI V6 biturbo (450 hp)
- Great potential and good robustness, but beware of:
- Hoses and cooling system → overheating possible if used intensively.
- Turbos : risk of wastegate fouling, loss of pressure at high mileage.
- High-pressure injectors sensitive to fouling (cleaning/removal sometimes necessary).
- Catalytic converters can become clogged with excessive urban driving.
- Faulty sensors (pressure, intake temperature) trigger engine warning lights.
- Generally reliable engine, but best suited for those with rigorous maintenance and a clear history.
Diesel
2.0 TDI (150-190 hp)
- Simple and widespread, but not without weaknesses:
- EGR : frequent clogging in urban use → loss of power / engine warning light.
- DPF : risk of saturation on short journeys (costly cleaning or replacement).
- Injectors : more sensitive after 150,000 km, symptoms = difficult starting / clicking.
- Water pump sometimes fragile (coolant leaks).
- On the road, it's a safe bet, especially the post-2018 versions with MHEV.
3.0 TDI V6 (218-272 hp and 347 hp for the S4 diesel)
- Considered one of the best engines in the B9 range.
- Points to be aware of:
- The timing chain is solid, but a metallic noise at startup should raise concern.
- EGR : always a sensitive issue, especially in urban use.
- DPF : can become clogged if poorly regenerated.
- EGR cooler : known leaks on some units → loss of coolant.
- Overall, reliable and durable if used appropriately (highway/long journeys).
Other known issues (all versions)
- S tronic / Tiptronic gearboxes : generally reliable, but check maintenance history.
- Power steering : rare leaks on some B9 models.
- Electronics : MMI sensors, driving assistance and parking radar can sometimes be temperamental.
- Front axle : silent blocks and suspension arms can wear out, especially on sport versions.
Upgrade and modernize your Audi A4, S4 or RS4 B9
The Audi A4 B9 already impresses with its refined design and perceived quality, but you can take it even further with our dedicated accessories. At Euro Racing Parts , you'll find everything you need to modernize and personalize your Audi : CarPlay/Android Auto modules for a more intuitive multimedia system;
We offer body parts in our shop: carbon mirror caps , rear diffusers , spoilers , and carbon interiors to enhance the passenger compartment:
We also offer replacement parts such as console buttons , gear knobs and many others:
All our products are compatible with the B9 generation and benefit from free delivery as well as a one-year warranty .
Which model should I choose?
- Daily use : 2.0 TDI post-2017 or 2.0 TFSI post-2017 (improved reliability).
- Reliable V6 diesel : 3.0 TDI, excellent performance/longevity ratio.
- Balanced sports car : S4 B9, powerful and relatively reliable supercharged V6 engine.
- Modern icon : RS4 B9, high-performing and technologically advanced, rigorous maintenance recommended.
