P0299 on Audi

The turbocharger on the 1.4 TFSI petrol A1 is a recognised weak point. The turbine/centre housing and bearings can fail, often aggravated by the engine's oil-consumption tendencies (oil starvation/coking of the turbo bearing). When it fails it produces a notable loss of power and smoke from the exhaust.

The BorgWarner BV43 variable-geometry turbocharger (OEM part 03L253056, BorgWarner 53039880208) can fail due to oil starvation, bearing wear, or variable geometry vane sticking/seizing. The most common failure mode is the variable vanes sticking or seizing, causing overboost or underboost. Catastrophic failures (compressor shaft snapping) are less common but documented. Failures typically occur around 100,000-150,000 miles.

The 2000-2002 C5 A6 Quattro 2.7T APB uses two position-specific turbochargers plus wastegate control, N75 regulation, recirculation valves, vacuum plumbing, charge-air hoses/intercoolers, crankcase ventilation, and separate oil/coolant connections. Low boost, noise, or exhaust smoke does not identify a turbocharger or a side by itself. Audi's diagnostic information specifically requires a leak-tight vacuum/charge system and notes that a recirculation valve or vacuum-line fault can produce no boost and rumbling. The previous card treated those symptoms as a predictable heat/oil failure across 2000-2004, added unsupported mileage and cost ranges, and sent every owner to a right-side 078145702R search before the failed component or bank was known.

The S7 with the 3.0T supercharged V6 (2012-2018) uses an electromagnetic clutch to engage the supercharger. Over time, the clutch disc wears out or the torsional isolator (damper) fails, creating a loud rattling, grinding, or "bag of marbles" sound from the front of the engine. This is most noticeable on cold starts or under load. A failed clutch prevents the supercharger from engaging, causing significant power loss. A failed isolator damages internal supercharger components, requiring complete supercharger replacement. Oil contamination accelerates wear—if oil becomes contaminated with dirt or debris, it causes premature failure of internal components. AudiWorld forums report failures between 60,000-120,000 miles, with repair costs of $1,500-$5,000.

Audi TSB 2070349/4 applies to 2019-2024 Q8 V6 TFSI vehicles with coolant loss, a coolant warning or an engine warning when the coolant pump is suspected. Audi requires precise leak confirmation: a small trace in the drip cup can be normal and dried deposits at the vacuum connection alone do not prove a leak. In individual confirmed cases, coolant can contaminate change-over valve N649 and produce P0299 as a secondary condition.

Current Audi TSB 2070349/4 applies only to 2021-2024 RS5 Coupe and RS5 Sportback V6 vehicles when the customer reports coolant loss/leak, a coolant warning or an engine warning and the workshop identifies the coolant pump as the leak source. Audi states that up to 3 ml of coolant on the pump drip cup over 100 operating hours can be normal seal lubrication/cooling. Dried coolant deposits on the vacuum connection alone are not clear evidence of a leak. Coolant contamination at change-over valve N649 may produce P0299 as a secondary condition. The bulletin does not support a universal turbocharger coolant-feed-line cracking defect or the frozen line part numbers.

The Audi S3 (2015-2020) uses the IHI IS20 turbocharger which develops a wastegate rattle due to wear in the wastegate arm pivot hole. The hole where the actuator arm peg fits wears open over time, allowing the wastegate flapper to vibrate loosely when not under boost. This creates a metallic rattling or buzzing noise, typically around 2,000-3,000 RPM under light throttle. In more severe cases, the electronic wastegate actuator itself fails, preventing proper boost regulation. Unlike earlier turbo designs, the IS20's wastegate actuator is integrated and cannot be serviced independently—requiring complete turbo replacement ($2,500-$4,000). Audi issued TSB 2027585/3 for a metal clip (06J145220A) to address early-stage rattle under warranty. PistonHeads and Audizine forums report this issue affecting approximately 20-30% of early 8V S3 models.

The water-to-air intercooler system on the S5 3.0T uses an electric coolant pump that can fail, causing elevated charge air temperatures and reduced power. Heat soak becomes severe in warm climates.

On certain 2013-2017 S7 vehicles, the turbocharger oil-supply strainer can block, starve the turbo bearings, and allow the shaft or turbine to fail, potentially stalling the engine.

The 4.0T's two turbochargers sit in the 'hot-V' between the cylinder banks, where trapped heat coks oil and wears the turbo bearings and wastegate hardware over time. A very common failure is wastegate-linkage wear: the hole in the wastegate arm where the actuator peg sits elongates, so the wastegate no longer seals tightly at rest. This produces a distinct metallic rattle on throttle-off or at idle and can cause boost-control problems and a P0299 underboost code. This is distinct from the NHTSA oil-strainer-blockage stall recall and from coolant-line failures — it is a mechanical wear issue of the turbo/wastegate itself in the heat-soaked hot-V location.

The S8 4.0T V8 shares coolant line issues with other 4.0T Audi models but the heavier sedan and higher power tune accelerate wear. Turbo oil and coolant line failures can cause expensive damage if not caught early.

The SQ5 3.0T supercharged V6 shares supercharger nose bearing issues with the S4/S5. The intercooler water pump also fails, causing heat soak and reduced performance, especially in warmer climates.

Audi identifies coolant loss from the mechanical coolant pump on 2018-2024 SQ5 V6 TFSI models. In some cases P0299 is logged when coolant entering the vacuum system impairs changeover valve N649. Audi cautions that a small trace on the pump drip cup can be normal and that dried deposits at the vacuum connection alone do not confirm a leak. This evidence does not establish an inherent design defect, a fixed failure mileage or a "when, not if" failure.