Audi S5 3.0 TFSI B9

The EA839 water pump uses vacuum actuation to control a slide valve inside the pump housing. When the internal seal degrades, coolant leaks into the vacuum system rather than externally, making the failure difficult to detect visually. The coolant can migrate to turbo wastegate actuators, brake booster lines, and the vacuum reservoir. Audi acknowledged this with TSB 2058890. Specialist shops report this regularly on cars from around 60,000-100,000 km. If caught early (unexplained coolant loss, P0299 underboost code), replacing the pump alone costs approximately 1,500-2,000 euros. If the vacuum system is contaminated, the repair escalates to 3,000-4,500 euros as multiple solenoid valves, lines, and the vacuum reservoir need replacement. The revised pump uses a 6-bolt pulley instead of the original 4-bolt design, making it easy to check visually. Audi has extended the piston skirt warranty to 8 years/130,000 km (EU), but the water pump itself is not specifically covered under this extension.

Early EA839 engines (produced before approximately August 2018) used rocker arms with small needle roller bearings that were undersized for the loads involved. Under sustained high RPM or high temperature conditions, the needle bearings can disintegrate and fall into the valve train, potentially damaging camshafts, cam position sensors, and cylinder head surfaces. The failure typically presents as a loud ticking noise, much louder than the normal injector/HPFP tick. Audi revised the rocker arm design with significantly larger bearings in mid-2018. Specialist repair at an independent shop runs approximately 3,000-5,000 euros depending on the extent of the damage. If Audi diagnoses severe damage, they may quote a full engine replacement at 15,000-25,000 euros, though specialists can usually repair the affected components for far less. This primarily affects 2017 and early 2018 production cars.

The Positive Crankcase Ventilation system uses a check valve integrated into the breather hose. When the internal membrane tears, crankcase pressure rises, which can blow the oil filler cap loose and spray oil over the engine bay. In severe cases this has led to small engine fires. Symptoms include a wandering idle between 1,000 and 2,500 RPM, a whistling noise from under the bonnet, and unusually strong suction when trying to remove the oil cap with the engine running. Audi issued a TSB with improved components for 2017-2019 models. The PCV solenoid valve part itself costs approximately 40-60 euros, but accessing the PCV system on the EA839 requires removing the intake manifold, bringing total repair costs to 400-800 euros at a specialist. If the turbocharger area also needs cleaning or attention due to oil contamination, costs can reach 1,200 euros.

The thermal management valve regulates coolant flow through various engine circuits for optimized warm-up and operating temperature. The internal diaphragm is prone to cracking, causing the valve to stick open or leak externally. This can also be triggered as secondary damage from a failed water pump pushing coolant into the vacuum system. Symptoms include intermittent overheating warnings, visible coolant drips near the valve, and fault codes P0597 or P2681. The valve itself costs approximately 80-120 euros, with labor adding 200-400 euros. Many owners do not notice the leak until it worsens, as initial leakage is often minimal. This failure is common enough that replacing it preventively during a water pump service is often recommended.

The plastic oil filter housing is positioned near the turbocharger wastegate actuator and is prone to developing leaks at the gasket surface. The leak can be mistaken for an oil pan leak due to oil running down the engine. On the EA839, accessing the housing requires partial removal of surrounding components, making this a labor-intensive repair. Parts cost approximately 100-200 euros, but labor runs 3-6 hours at a specialist. At an Audi dealer, total cost can reach 1,200-1,500 euros. Many independent specialists can complete the job for 500-800 euros. This issue typically appears from around 80,000 km onward.

The B9 S5 uses electronically controlled hydraulic engine mounts designed to balance engine support with cabin refinement. These mounts are filled with hydraulic fluid that can leak as the rubber seals age. Failed mounts produce noticeable vibrations at idle (particularly in Drive at a standstill), clunking when engaging Drive or Reverse, and increased NVH at low speeds. Mounts typically last 80,000-120,000 km depending on driving style. Replacement costs approximately 200-250 euros per mount for OEM parts, with labor at 2-3 hours per side. Total cost for a pair is approximately 600-900 euros at a specialist, somewhat less if only one mount has failed.

A documented design limitation in the EA839 engine involves piston instability (rocking) within the cylinder bore. Machined oil drain holes act as stress risers, and over time, cyclic loading can cause cracks in the ringland area. This leads to combustion gas leakage and piston damage. While dramatic, the observed failure rate is well below 5% and Audi has released three piston revisions, indicating they acknowledge the issue. One dealership reported 14 cases in a 6-week period, but across the entire EA839 production this remains rare. Audi has extended the piston skirt warranty to 8 years/130,000 km (approximately 80,000 miles) in Europe, transferable to subsequent owners. Signs include unusual oil consumption (more than 1L per 5,000 km), blue exhaust smoke, and misfires. If the failure occurs outside warranty, repair typically requires a partial or full engine rebuild costing 5,000-15,000 euros depending on the extent of damage.