When buying a used Audi A4 3.0 TDI 2018 (B9), the most frequently mentioned issue: Coolant leaks and failures in the engine V area. Also, recurring MAF sensor failure (implausible signal) is commonly reported.
Good summary
Most reported issue: Coolant leaks and failures in the engine V area. Service history and a test drive matter.
Listed from most frequently reported, each with its source.
Leaks from the valve/pipe group in the V area (e.g., thermostat valve/coolant control valve) and EGR cooler gaskets can lead to overheating, warning lights, and costly repairs due to difficult access.
Cooling
Several users report an 'implausible MAF signal' error (G70/MAF); this error may return even after sensor replacement. The issue manifests with fault codes, limp mode, or power fluctuations.
Engine Bay
Some users report premature wear of timing components (chains, tensioners) or camshaft/camshaft bearings in EA897 versions; this causes noises (cold rattling) during startup and can lead to major repairs if left untreated.
Timing chain
In newer 3.0 TDI engines, failures in the exhaust aftertreatment system (NOx sensor, AdBlue/urea pump/actuator, dosing valves) are reported. Symptoms include intermittent emission warning lights and failing emissions tests; repairs can be expensive.
Exhaust Emissions
Carbon buildup in the EGR valve and exhaust gas recirculation circuits can cause uneven power delivery, P040x fault codes, and power loss at low/mid RPMs.
Exhaust Emissions
The turbocharger and its electronic actuator may have limited lifespan under hard driving or neglected maintenance; issues with front/crank pulley, oil leaks from turbo pipes, and wear are reported.
Turbo
Audi A4 3.0 TDI (2018): boot 425 L; fuel use 5,5 l/100 km (urban 5,2 l/100 km · extra-urban 4 l/100 km); 0–100 in 10.4 s.
Same trim, different year
We only publish claims we can verify. Cards come from Difetti fault records matched to this vehicle on brand, fuel, engine and generation.