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 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.

The factory water pump on the EA839 3.0L V6 TFSI (and 2.9L on RS Q8) has an inherent design flaw. The pump uses engine vacuum to actuate a slide valve that controls the impeller. As the internal seal degrades, coolant is drawn internally into the engine's vacuum system and/or leaks externally onto the front of the block and bank-one cylinder head. This causes gradual coolant loss, can contaminate vacuum lines, and in severe cases leads to overheating or a drivetrain-malfunction limp mode. Audi addressed it with a redesigned 6-bolt pulley pump (replacing the failure-prone 4-bolt unit). Documented in Audi TSB referencing 'loss of coolant from coolant pump.'

The RS Q8 4.0T twin-turbo V8 generates significant heat in the enclosed SUV engine bay. Reduced airflow compared to sedans and higher coolant temperatures accelerate coolant line and connection degradation.

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 B5 S4 2.7L twin-turbo V6 is notorious for turbo failure due to oil starvation from coked oil feed lines. Both KO3 turbos can fail, with the rear turbo being particularly difficult to access for replacement.

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.

The S7 shares the 4.0T biturbo V8 cooling system issues with turbo coolant lines cracking under heat cycling. The thermostat housing also cracks, causing slow coolant loss that is hard to detect.

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 Audi S7 (2012-2017) with the 4.0T twin-turbo V8 has a critical design flaw in the turbocharger oil supply system. A poorly designed oil strainer (screen) collects oil sludge and carbon deposits, blocking oil flow to the turbocharger bearings. Oil-starved turbo bearings fail, causing the turbine wheel to contact the housing or the turbo shaft to break. This leads to sudden engine stall while driving—including on highways—with the engine unable to restart. NHTSA received 58 complaints and opened an investigation. Audi received 1,889 warranty claims and 47 field reports. NHTSA Recall 22V178 covers 2013-2017 S6, S7, RS7, A8, and S8 models. Audi extended the turbocharger warranty to 10 years/120,000 miles and will replace the oil strainer with a larger-mesh version. Vehicles built after March 30, 2017 already have the updated screen.

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.

The SQ8 4.0T V8 turbo coolant lines suffer from the same heat-cycle degradation as other 4.0T Audi models. The SUV packaging increases underhood heat, accelerating line and connection failure.