Audi A5 40 TFSI B9

The EA888 Gen 3B uses an integrated water pump and thermostat housing made partly of plastic. The O-ring seal swells from oil exposure over time, and the plastic housing can crack under thermal cycling. Symptoms include low coolant warnings, puddles under the car, and erratic temperature readings. This is the most commonly reported failure on B9 2.0 TFSI engines across A4, A5, and Q5 forums. Many owners report the issue appearing between 60,000 and 100,000 km, though some early examples fail as early as 40,000 km. When one component fails, specialists recommend replacing both the water pump and thermostat housing together due to the integrated design. Independent shop repair costs approximately 800 to 1,100 euros (parts 350 to 500 euros, labor approximately 3.5 hours). Audi dealers typically quote 1,300 to 1,500 euros. Aluminium aftermarket housings from GRAF or similar are more durable than the original plastic. Audi has offered extended warranty coverage for this component on some VINs for 8 years from in-service date — always check with your dealer before paying out of pocket.

All direct-injection TFSI engines are susceptible to carbon buildup because fuel is injected directly into the combustion chamber rather than over the valve surfaces. Carbon from crankcase vapours gradually accumulates on the intake valves, restricting airflow. Symptoms develop gradually: rough idle (especially when cold), hesitation during acceleration, minor misfires, and reduced power. These typically become noticeable between 80,000 and 120,000 km. Walnut shell blasting is the standard cleaning method. Independent specialists charge 600 to 800 euros, while Audi dealers charge 1,000 to 1,500 euros. This is not a defect but an inherent characteristic of direct-injection engines and should be treated as periodic maintenance. Short trips and gentle city driving accelerate the buildup. Using quality oil and occasional spirited driving helps slow the process but does not prevent it entirely. The 40 TFSI does not have supplementary port injection, so it is fully susceptible.

Most A5 B9 40 TFSI models use the DL382 7-speed S-tronic, a wet-clutch dual-clutch gearbox. While significantly more reliable than the smaller DQ200 dry-clutch unit, it can still develop issues. Common symptoms include jerky 1st-to-2nd gear shifts at low speed, delayed engagement from standstill, and occasional gearbox malfunction warnings. The mechatronic unit (electronic valve body) can fail, with the driver position sensor (G676) being a documented weak point. Problems typically appear between 80,000 and 120,000 km, especially if the transmission fluid was never changed. Audi officially considers it a lifetime fill, but specialists unanimously recommend changing the fluid every 60,000 km. Mechatronic repair at a specialist costs 1,200 to 2,000 euros. Full gearbox rebuild runs 2,500 to 3,500 euros. Manual gearbox cars (rare in the B9 A5) are not affected.

The PCV valve on the EA888 Gen 3B contains a rubber diaphragm that deteriorates over time, typically between 70,000 and 120,000 km. When it tears, symptoms include rough idle, a hissing or whistling noise from the engine bay, increased oil consumption, boost leaks causing power loss, and check engine light with lean or rich mixture codes. Diagnosis is straightforward: check for vacuum at the PCV breather port cap. The valve itself costs 50 to 80 euros for an OEM replacement. Labor requires removing intake components and takes approximately 2 to 3 hours. Total repair at an independent shop runs 250 to 350 euros, Audi dealers charge 400 to 500 euros. A failed PCV valve also accelerates carbon buildup on the intake valves, so it should be addressed promptly.

The turbo wastegate actuator develops a rattle as the internal bushing wears, most audible during acceleration between 1,800 and 3,000 RPM. This is typically a cosmetic annoyance rather than a performance issue. Volkswagen issued a Technical Service Bulletin (TSB 2024061) recommending installation of a rattle clip (part 06J145220A) to eliminate the noise, costing under 50 euros at most shops. If the actuator mechanism itself has seized, actuator replacement costs 200 to 500 euros at an independent specialist. Full turbo replacement is rarely necessary unless the turbo internals have been damaged from extended operation with a stuck wastegate.

The A5 B9 uses a complex multi-link front suspension with aluminium control arms. The rubber bushings deteriorate over time, particularly on cars driven on rough roads. Symptoms include clunking or squeaking over bumps, vague steering feel, and uneven inner front tire wear. This is a wear item rather than a design defect, typically appearing after 80,000 to 120,000 km. Most mechanics recommend replacing complete control arms rather than pressing in new bushings, as the labour difference is minimal. A quality aftermarket control arm kit for both sides (Lemforder or Meyle HD) costs 300 to 500 euros in parts. Independent shop total runs 500 to 800 euros; Audi dealer quotes reach 1,000 to 1,200 euros. Wheel alignment is essential after replacement.

LED headlights develop condensation more readily than traditional bulbs because LEDs emit far less heat. Audi's own TSB and the owner's manual state that light misting is a normal characteristic, as the headlights are ventilated systems. The moisture should clear after a motorway drive with low beams on. However, when water droplets pool at the bottom of the housing rather than just misting the lens, this indicates faulty seals or blocked air vents. Early B9 cars (2016-2017) have a higher incidence due to the vent design. Seal repair typically costs 200 to 400 euros per headlight. Full headlight assembly replacement is 600 to 800 euros per side if seals cannot be restored.