The brand-new 3.0L TFSI Supercharged V6 that came with the B8 S4 was introduced in late 2008. The Eaton supercharger for the B8 S4 was installed between the block’s “Vee” and was cooled by two independent water-to-air intercoolers. The Audi B8 S4, which had just six cylinders and a slightly smaller engine, almost equalled the performance figures of its predecessor, the B7, with 329 horsepower and 325 lb-ft of torque.
The B8 S4 had a makeover at the beginning of 2012 that included aesthetic and mechanical improvements. To distinguish the two vehicles clearly in the eyes of the Audi community, post-facelift versions are referred to as B8.5 S4s.
Before getting into particular issues with the B8 S4, let’s talk about how the B8.5 stacks up regarding dependability.
For the B8 A4’s most typical problems:
Audi B8 reliability vs. B8.5
The B8.5 S4s are generally regarded as being substantially more dependable than the B8 S4s. The DSG or “S-Tronic” transmissions were one of the significant B8 model flaws. Because of design flaws, the dispatches encountered problems with mechatronics. In 2012, the B8.5 cars were upgraded to the next generation of DSG gearbox, which resolved these issues.
Aside from the common problems that most Audis have, including coil pack problems, there aren’t any significant failure spots for B8.5 models. The gearbox remains a high-failure site for S4s that have not upgraded their pricey mechatronic components with defect-free ones. Thus the same cannot be stated for the B8 generations. Aside from this, the B8s are susceptible to the same problems with coil packs, thermostats, and water pumps. Late in 2010 or early in 2011, an improvement was made to the water pump, which decreased the likelihood of it failing.
Overall, the B8.5 is more dependable and less troublesome due to the gearbox and water pump issues in previous year B8 vehicles.
Audi B8 S4 Problems
- S-Tronic / DSG Gearbox
- Water pump problems
- Excessive Oil Burn / PCV Valve
- Carbon accumulation
- Injector, coil, and spark plug misfire
1. An Issue With The B8 S4’s DSG Or S-Tronic Gearbox
According to estimates, the DSG gearboxes in as much as 20% of B8 S4 vehicles had issues. Most of the problems were caused by the Mechatronics unit breaking down and having to be replaced, which costs at least $4,000 to fix. The oil-cooled system’s mechatronics unit, which regulates shifting, causes circuit board problems. The device would fail due to oil interacting with the board and heating up, causing jerky gear changes.
Most likely, the mechatronics unit will break down after 20k miles. However, locating a B8 S4 with fewer than 20,000 miles on the odometer is probably challenging today, so I would verify that this issue was resolved before buying a pre-2012 B8. The mechatronics failure concerns were settled in 2012 when Audi changed the gearbox to a “Gen II” DSG transmission in conjunction with the B8.5 facelift. This improvement allowed for the resolution of the difficulties.
The gear shift sensor, separate from the mechatronics unit, was prone to malfunction, which might result in a warning reading “Gearbox Malfunction – You Can Keep Driving.” In addition, there is a possibility of an early clutch pack failure, although this issue seems unusual.
2. B8 S4 Water Pump Failure
Audis are infamous for having frequent water pump issues. Not to worry; BMWs also have this issue. The B8 S4 has a high propensity for unexpectedly systematic and early water pump failure.
The water pumps use an impeller to push fluids via the cooling system and through the water pump. The plastic impellers were haphazardly constructed, making them more prone to breakdown over time since they work in a highly pressured environment. When the impeller breaks, the water pump cannot pump coolant via the cooling system. Your engine overheats, and your vehicle becomes stranded on the side of the road, awaiting a tow truck.
Symptoms of Water Pump Failure – B8 S4 Engine Overheating
- Overheating engine
- Engine coolant is low
- Smoke appearing from the engine bay
- Leaking coolant from the engine bay
- Check engine light, codes: P2181, P3081, P00B7, P0087, etc.
Investing in a new water pump with a metal impeller is the least complicated way to replace the old one. A water pump’s original equipment manufacturer (OEM) is notorious for failing every 50,000 to 80,000 miles. It will likely keep breaking down if OEM pumps are constantly swapped out to fix it. Metal impeller water pumps eliminate any concerns brought on by plastic impeller water pumps, making them more dependable.
The thermostat and the water pump are other standard failing parts in B8 S4s. A typical cause of engine overheating is a thermostat that becomes stuck in a locked state, blocking the flow of coolant to the engine.
3. PCV Valve in B8 S4 Failed
The “positive crankcase ventilation” valve is known as the PCV valve. Engines produce harmful gases as a natural byproduct, which are detrimental to the environment. To ensure that these gases are wholly burnt off, the PCV valve will recirculate them into the combustion chamber. These gases are harmful to the atmosphere, but they also cause carbon and other “sludge” to accumulate in your engine, which may reduce its performance and efficiency.
Your B8 S4 may have performance troubles due to a faulty PCV valve. Misfires, high oil use, low AFRs, and oil leaks are some typical issues brought on by a malfunctioning PCV valve. High oil consumption is one of the most apparent symptoms of a faulty PCV valve on the B8 S4. According to owners, one litre of oil is typically used every 1,500 – 2,000 miles.
B8 S4 Symptoms of a Failing PCV Valve
- Erratic idling and misfires
- When accelerating, the engine makes whining noises.
- Lean air-to-fuel ratios
- Engine fault codes P0171 and P0507 displaying
4. B8 S4 Carbon Buildup
The S4 employs direct injection, much as every other contemporary Audi. Audi prefers to refer to it as “stratified injection,” thus the names TSI, FSI, and TFSI. In contrast to port-injection systems, which pump fuel into the intake valves, direct injection systems feed gasoline directly into the cylinders. High-pressure gasoline is shot into the engine. Thus, a port-injection engine’s intake valves are cleaned by highly compressed gas.
Final Thoughts
The Audi B8 S4 can be reliable, provided it is properly maintained. Common issues such as water pump failure, PCV valve problems, and carbon buildup can be avoided by regularly servicing your car and investing in quality parts when needed. If you encounter issues with your B8 S4, take it to a reputable mechanic for evaluation and repair. Contact our network of Audi breakers across the UK for competitive quotes if you need any parts.
