Unpacking the Audi S5: Common Faults & Fixes

The Audi S5, a sophisticated blend of performance and luxury, often captivates drivers with its sleek design and potent engines. Positioned as the high-performance sibling to the A5 coupe and a more practical daily driver than the hardcore RS 5, it promises an exhilarating experience. However, like any complex piece of German engineering, the S5 has its share of common foibles that potential buyers and current owners should be aware of. This deep dive will explore these prevalent issues, offering insights into symptoms, potential solutions, and estimated repair costs, ensuring you're well-equipped to navigate the world of S5 ownership.

Carbon Buildup: The Lingering Legacy of Direct Injection

One of the most widely reported issues, particularly in early models, is excessive carbon buildup. The 4.2 V8 FSI engine, found in S5 coupe models from 2008 to 2012, is particularly notorious. These engines utilised early forms of direct injection, spraying fuel directly into the combustion chamber. Consequently, fuel didn't wash over the intake valves, leading to carbon deposits accumulating over time, often becoming noticeable after around 60,000 miles.

While the supercharged 3.0-litre V6, which replaced the V8 from 2013 to 2017 (and was also in early S5 convertible models from 2010), is less prone, it can still suffer from carbon buildup, typically at higher mileages. The symptoms are unmistakable:

• Misfires and rough running
• Poor fuel economy
• Shaking or vibration at higher RPM
• The car entering 'limp mode'
• Illumination of the 'check engine' light

Owners frequently report these issues. One A5OC.com member described their 2009 S5 4.2 V8 with just 35k miles experiencing the 'dreaded carbon buildup,' leading to P2006 and P2007 error codes. Another on AudiWorld.com recounted their 2010 S5 at 74k miles, where a blinking engine light and engine shuddering led to injector replacement and the discovery of significant carbon on the intake valves, with some deposits reportedly up to 5mm thick.

The most effective remedy is professional walnut blasting of the intake valves. This process typically costs around $500 (US dollars) at an independent Audi or European car specialist, with many enthusiasts recommending it every 60,000 to 100,000 miles. For the DIY enthusiast, removing the intake manifold and carefully scraping off deposits after softening them with solvent is an option. Using premium fuel and driving the car 'spiritedly' to ensure optimal engine temperatures can help mitigate, but not eliminate, the issue.

Coolant Leaks: The Peril of Plastic Components

Coolant leaks are a very common problem across all S5 model years, often stemming from cracked water pumps and thermostat housings. Many of these crucial components, along with various pipes and fittings, are made from plastic, which inevitably becomes brittle and cracks with age and heat cycles.

Signs of a coolant leak include:

• Low coolant warning light
• An empty or significantly depleted coolant reservoir
• Visible puddles of coolant under the car
• The distinct smell of burnt coolant
• Engine overheating issues
• A heater that fails to warm the cabin

The V8 engine's thermostat is also prone to failure, getting stuck and causing overheating even without visible leaks. Audizine.com users frequently share similar experiences; a 2012 S5 owner described a sudden overheating incident, diagnosed as a bad thermostat and potentially water pump after no leaks were found under pressure test. Another 2013 S5 owner faced a similar overheating scenario on the motorway, resulting in a dealership repair estimate of around $1,900 (US dollars) for a new thermostat and water pump.

Despite Audi and Volkswagen revising the thermostat housing multiple times, the issue persists, particularly in older vehicles. An out-of-warranty repair for a water pump and thermostat assembly alone costs approximately $400 (US dollars). Labour can significantly increase this. For B8.5 models with the 3.0-litre V6, replacing these components is more complex as the supercharger must be removed. In B9 S5 models (2018 onwards), the front bumper needs to be removed. Dealership costs can easily exceed $1,000 (US dollars), making an independent specialist a more budget-friendly option.

PCV Issues: Crankcase Ventilation Headaches

The PCV (Positive Crankcase Ventilation) valve, also known as the air oil separator, is another common failure point for various S5 model years, often before the 100,000-mile mark. This emissions control system recirculates harmful 'blowby' gases back into the engine for cleaner combustion. When it fails, it can disrupt the air-fuel mixture and cause excessive pressure in the crankcase, leading to premature wear of seals and gaskets. The PCV valve, being plastic, can also crack, allowing coolant to mix with oil.

Symptoms of a faulty PCV valve include:

• Rough idling
• Engine misfires
• Hissing or whistling noises from the engine bay
• Coolant mixing with engine oil
• Low coolant levels
• Rear main seal leaks
• Excessive oil consumption
• Difficulty removing the oil cap due to strong suction

A 2014 S5 owner on A5OC.com reported a PCV fault and strong suction when attempting to remove the oil cap with the engine running, alongside a rough idle. The 2017 to 2019 S5 models also experienced premature failure of the PCV breather hose. An Audizine.com user with a 2018 B9 S5 Sportback described their car 'bogging' during deceleration, a 'wandering/hunting idle,' and a loud whistling sound, all pointing to a PCV unit failure creating a significant vacuum leak.

Audi has updated the breather line for 2017-2019 models with an improved membrane. A new PCV valve and associated parts typically cost around $100 to $200 (US dollars). While a relatively simple repair on the 4.2 V8, the 3.0-litre V6 models require supercharger or turbocharger removal, pushing total repair costs past $1,000 (US dollars). Many B8 and B8.5 S5 owners wisely choose to replace the PCV and water pump simultaneously to save on future labour costs, as both components are known to fail and are accessible once the supercharger is out.

Timing Chain Issues: The Cold Start Rattle

Older S5 models equipped with the supercharged 3.0-litre V6 (specifically 2011 to 2014) can develop a characteristic rattle on startup, often due to issues with the timing chain tensioner. This rattle is typically heard only after a cold start and usually lasts a mere 1 to 3 seconds. While a persistent, long-lasting rattle might indicate a stretched timing chain or severely worn guides, actual reports of catastrophic timing chain failures are quite rare in the S5, unlike the 4.2 V8 in the older S4.

Potential symptoms of a stretched timing chain include:

• Engine rattle (especially on cold start)
• Misfires and rough idling
• Difficulty starting the engine
• Engine stalling
• Reduced engine power
• Illumination of the 'check engine' light
• Timing-related trouble codes

Owners on AudiWorld.com have shared their concerns; a 2015 S5 owner with only 43k miles reported a rough idle and rattling noise, diagnosed as a driver bank timing chain tensioner issue, with an independent shop quoting around $2,500 (US dollars) for replacement of both sides. Another owner's 2013 S5 3.0t suffered from a noisy start, attributed to the driver-side chain tensioner (TSB 2039995/1), with an initial dealership quote of $9,300 (US dollars) that was later revised to $4,800 (US dollars).

Audi did issue a Technical Service Bulletin (TSB) for V6 3.0 TFSI engines, recommending the replacement of the old timing chain tensioner with an updated part to eliminate the rattle. The TSB suggested the rattle wouldn't lead to other issues, but this isn't a guarantee, especially for high-mileage or poorly maintained cars. Replacing the timing chain and tensioners is an 'engine out' repair, potentially costing over $5,000 (US dollars) at a dealer. An independent specialist could significantly reduce this cost.

Crank Pulley Failure: A Disintegrating Drive

The crankshaft pulley on the Audi S5’s 3.0-litre supercharged V6 has a propensity to break apart and separate. This failure can damage the serpentine belt and other accessories located at the front of the engine. When the crank pulley fails and the serpentine belt breaks, the supercharger loses its drive, resulting in no boost, and the power steering will also cease to function. This issue is more prevalent in early models from 2010 to 2013 but can affect newer cars too, even with updated pulleys. The B8 and B8.5 Audi S4 models also report numerous crank pulley failures.

An owner with a 2013 S5 on Audizine.com described their 'B8.5 crank pulley failure at 57k,' where the pulley failed, causing both belts to slide forward, with the supercharger belt eventually flying off and the accessory belt snapping after partially wrapping around the supercharger pulley.

A new genuine Audi crankshaft pulley costs around $500 (US dollars), while aftermarket alternatives are considerably cheaper, often around $200 (US dollars). Some owners opt to replace the factory two-piece design with more durable aftermarket single-piece units. Beyond the pulley itself, you'll likely need to replace the serpentine belt and any other components damaged in the incident. An independent Audi specialist can typically complete the pulley replacement and any minor associated repairs in about two hours, provided no other major parts are damaged.

Rocker Arm Failure: B9 Engine Catastrophe

Early model years of the B9 Audi S5 (2018 to 2019) have seen a small number of cars suffer from rocker arm failures, which can lead to severe engine damage. While not widespread, the potential for high repair costs makes this a significant concern. A key symptom of failing rocker arms is a loud ticking sound, noticeably louder and more distinct than the normal ticking from injectors or the high-pressure fuel pump. Continued driving with this issue can cause the rocker arms to wear excessively, sending harmful metal shavings throughout the engine.

An S5 owner on AudiWorld.com recounted their 2018 S5's visit to an Audi dealer after noticing a rougher idle and a louder-than-usual ticking sound. The devastating news followed: 'metal shavings in your oil.' Despite being covered under warranty, the repair involved replacing both sets of 12 roller rockers (24 in total) and took nine weeks due to parts availability. The dealer believed damage to one rocker arm was the source of the metal shavings.

Replacing rocker arms at a dealership can easily cost $10,000 (US dollars) or more, as it necessitates a significant engine tear-down and rebuild of the cylinder head. The parts alone are around $1,500 (US dollars). An independent Audi specialist might perform the repair for approximately $5,000 (US dollars) or less. If the engine is damaged beyond repair and you're out of warranty, sourcing a used engine for a swap might be the most economical solution. It's worth noting that many enthusiasts consider this issue somewhat 'overblown,' given the very small percentage of vehicles affected relative to the total S5 sales.

Dual-Clutch Transmission Issues: S-tronic Woes

The 7-speed S-tronic dual-clutch transmission (also known as DSG), found in early models of the S5 convertible, is prone to failure, often due to mechatronic unit problems. The mechatronic unit is the electro-mechanical heart of the gearbox, controlling gear shifts. Failures are more common in 2010 to 2012 S5 convertibles, though early 2013 coupe and convertible models can also be affected. Early V8-engined S5 coupes came with a traditional automatic, so they are immune to these specific DSG issues. The S-tronic was exclusively paired with the V6 models of the first-generation Audi S5, and even 2013 and newer RS 5 models can suffer similar DSG problems.

Common symptoms of a faulty mechatronic unit include:

• Rough or hard gear shifts
• Jerky acceleration, especially at low speeds
• Inability to select reverse gear
• Difficulty shifting into certain gears or losing gears entirely
• The transmission unexpectedly shifting into neutral
• Hesitation during acceleration
• The dreaded 'gearbox malfunction' warning

An AudiWorld.com user with a 2011 Audi S5 DSG 7-speed transmission reported the 'gearbox malfunction' code, hard shifts, occasional loss of reverse, and the car entering limp mode. Another owner with a 2011 S5 3.0 cabriolet experienced similar issues, including rough shifts, TPMS sensor activation, and loss of reverse and drive, along with the error code P17D5 00 [096] – Valve 3 in Transmission Part 2 Mechanical Malfunction. This owner had their mechatronics replaced, with little improvement, and was then quoted for a full transmission replacement.

Regular servicing of the S-tronic transmission with fresh fluid every 40,000 miles is crucial to prevent premature failures. However, even well-maintained pre-facelift B8 cars can still experience mechatronic unit failure. If problems arise, a fluid and filter change might resolve minor issues, but the DSG is highly sensitive to correct fluid levels. Mechatronic repair kits, costing around $800 (US dollars), can sometimes fix gearbox problems. Replacing the entire mechatronic unit typically costs $2,000 to $3,000 (US dollars), while a new transmission can easily exceed $5,000 (US dollars).

Suspension Issues: Wear and Tear

The Audi S5's suspension components, particularly ball joints and control arm bushings, can wear out at relatively lower mileages. This wear eventually leads to noticeable problems with the car's ride and handling.

Symptoms of worn suspension components include:

• Creaking or clicking sounds, especially over bumps
• Uneven tyre wear
• Vibrations felt through the steering wheel
• Degraded handling and steering precision
• Persistent alignment problems

AudiWorld.com owners frequently report these issues. A 2014 S5 owner with 40k miles was informed by their mechanic that all four upper control arm bushings needed replacement. Another with an '09 S5 V8 at 39k km found cracking in the bushings of all front control arms. Unfortunately, Audi typically sells entire control arms rather than just the bushings, making repairs more expensive.

New genuine Audi control arms are quite costly, ranging from $300 to $500 (US dollars) per piece. Dealership replacement costs can easily exceed $1,000 (US dollars) due to labour. Aftermarket complete kits are more affordable, costing around $500 to $700 (US dollars). While individual bushings are inexpensive, replacing them requires significant effort and a hydraulic press. Opting to replace the entire control arm also addresses any associated ball joint issues.

Sunroof Issues: Squeaks and Rattles

A number of second-generation Audi S5 owners (B9) have reported persistent squeaks and rattles emanating from the sunroof. These noises tend to manifest when driving on uneven roads or up driveway ramps, causing the chassis to flex and allowing various parts to rub against each other.

AudiWorld.com users have described their frustrations. A 2018 S5 coupe owner battled a 'creaking noise like hard plastic rubbing on hard plastic' from the rear of the moonroof, requiring three dealership visits and the addition of felt padding and a new trim piece to mostly resolve the issue. Another owner of a 2018 S5 experienced a rattle from the sunroof when open, a problem that persisted even after their original S5 was replaced by Audi due to multiple faults.

Over time, the continuous stress from chassis flex can also lead to more serious problems, such as cracking of the sunroof frame itself. Replacing a sunroof frame out of warranty can cost around $1,000 (US dollars). In some cases, owners resort to creative DIY solutions, such as applying lubricant or strategically placing foam between offending parts to dampen the noise.

Window Issues: The Constant Motion Problem

The Audi S5's window motors and regulators tend to have a shorter lifespan than expected due to their constant operation. The frameless windows are designed to drop slightly whenever the doors are opened to clear the sill and ease closing, then roll back up when the doors are shut to create a seal. This constant up-and-down motion eventually takes its toll, leading to premature burnout of the window motors or regulators.

AudiWorld.com owners have reported various window malfunctions. A 2018 Audi S5 owner noticed the window rolling down unexpectedly when trying to close it. Another's issue wasn't resolved until the window control unit was replaced after four dealership visits, and even then, intermittent problems persisted. A coupé owner described their power windows as 'intermittently flaky,' eventually developing an issue where the driver's side window would drop several inches upon opening either door, and then only rise 1 cm when closed.

A new genuine Audi window motor is quite expensive, typically around $400 (US dollars). Aftermarket replacements offer a more budget-friendly option, ranging from $50 to $200 (US dollars). Window problems can also stem from a faulty door control module, a blown fuse, or other electrical wiring issues. Often, a simple reset procedure – fully opening the windows, holding the button for 10 seconds, then fully closing them and holding the button for another 10 seconds – can resolve minor glitches.

Speaker Issues: B9 Audio Disappointment

A number of second-generation S5 owners, particularly those with the four-door Sportback model from 2018 onwards, have voiced complaints regarding the quality of the factory sound system. These complaints are also prevalent in the regular A5 and RS 5 Sportback models, with many feeling a distinct lack of bass output.

An Audizine.com owner, upon receiving their '20 S5 Sportback with the Bang & Olufsen system, immediately noted how 'underwhelming the audio sounded,' specifically highlighting 'the lack of bass/punch to the music.'

Several owners eventually discovered that the subwoofer in the rear was wired incorrectly, operating out of phase and resulting in a thin, lifeless bass response. The fix is relatively simple: reversing the two subwoofer wires and soldering them correctly. Beyond this, many owners have also complained about rattling from the door and centre speakers, which could be attributed to loose fasteners or inadequate sound dampening. Some have only found relief by replacing the factory speakers with higher-quality aftermarket alternatives.

Summary of Common Audi S5 Issues

To provide a quick overview, here’s a table summarising the most common problems encountered by Audi S5 owners:

Audi S5 Pros & Cons

Despite its potential issues, the Audi S5 remains a highly desirable vehicle for many. Here's a balanced view:

Pros:

• Stylish exterior: A truly handsome car with timeless appeal.
• Upscale cabin: High-quality materials and excellent build quality define the interior.
• Quick acceleration: Both V8 and V6 engines deliver impressive power and pace.
• Confident handling: Engaging to drive, especially on twisty roads, with good roadholding.
• Comfortable ride: Manages to balance sportiness with everyday comfort remarkably well.
• All-wheel drive: Audi's Quattro system provides superb traction and stability in various conditions.
• Modern tech and creature comforts: Equipped with a good array of technology for convenience and entertainment.

Cons:

• Expensive parts and maintenance: German luxury cars come with premium repair costs.
• Limited interior storage: Practicality can be a minor compromise in some variants.
• Rivals have more extreme performance: While quick, dedicated sports cars might offer a more raw, track-focused experience.

What Do The Reviews Say?

Overall, reviews for the Audi S5 are largely positive, praising its balanced nature. Edmunds, for example, notes that 'the S5 is very balanced for both performance and luxury. It’s a beautiful vehicle inside and out and has easy-to-use controls. It’s genuinely enjoyable if you want to take it on twisty roads, and it doesn’t sacrifice comfort and luxury.'

Reviewers frequently highlight the powertrain: 'There’s plenty of power from the turbocharged V6 even if it’s not immediately explosive off the line. Once on the move, acceleration is swift, steady and satisfying.' The handling also receives acclaim: 'The S5 is capable around corners too. Our car came equipped with the optional S Sport package. It helps blend the best of all-wheel-drive traction with the nimble feeling of a rear-wheel-drive car. The S5’s dynamic steering also feels well matched to whatever drive mode setting you’re in.'

Comfort and practicality are often lauded, particularly for the Sportback: 'We continue to be amazed at the balance of the S5 Sportback. Comfort is just as much a priority as performance. The front seats are very supportive and pleasant, and the available heated and ventilated elements work swiftly.' Regarding space, 'Getting in and out of the S5 Sportback’s front seats is easy. If you’re on the taller side, you might have to duck to get into the rear seats due to the sloping roofline. There’s a good amount of room for front occupants plus plenty of adjustment range for the driver. The rear seats are decent in terms of comfort and space for two adults up to about 5-foot-10 or so.'

What’s the Resale Value of an Audi S5?

The resale value of an Audi S5, like any luxury performance car, depreciates over time, but it generally holds its value reasonably well compared to some rivals. Here’s a snapshot of used car pricing on Edmunds (prices in US dollars, accurate at the time of writing):

Engine Rebuilds: A Second Life for Your S5

For S5 owners facing significant engine issues, particularly with the 4.2-litre V8, a full engine rebuild can be a viable and often more cost-effective alternative to sourcing a new engine. Specialists like AMTuned offer comprehensive engine building services, from factory-style refreshes to high-performance upgrades.

AMTuned, for instance, highlights their expertise in sleeving Audi hypereutectic blocks, allowing them to maintain factory bore sizes even for high-power applications. This proprietary process, utilising custom-specification sleeves manufactured by LA Sleeve, reportedly creates more powerful engines with factory displacement and mitigates the risk of coolant leaks from cracked vapour ports between the bores.

Their services typically involve:

• Fully sleeved engine block: Diamond hone finish with a plateau final hone for expedited break-in.
• Cylinder head refresh: Cleaning, inspection, new guides, upgraded valve guide seals, gaskets, valve testing, skimming of mating surfaces, and pressure testing.
• Engine block refresh: Cleaning, new main and connecting rod bearings, piston rings, lower engine o-rings, and all new gaskets/seals.
• Complete timing service: Utilising OEM and OE parts.

They offer various 'stages' of rebuilds, from a 'Stage 0 Sleeved' refresh for the BNS / BYH / CAUA 4.2L 32V engine, to 'Stage 1, 2, and 3 Sleeved' options for those seeking higher safeguards for forced induction or extreme power. Turnaround times typically range from 12-18 weeks. Customers must contact them prior to shipping and purchase the rebuild stage in full. Shipping costs (typically $275-$500 one way within the continental US) are not included, but local drop-off is available.

It's important to note that accessories (oil filter housing, water pump, power steering pump, A/C compressor, alternator, etc.) must be removed before shipping. AMTuned reuses camshaft phasers, so owners with known phaser issues should arrange for replacement at an additional cost. They offer a 24-month warranty on stage engine builds not used with aftermarket forced induction systems, as custom tuning issues are outside their control. This warranty does not cover fuel injection-related failures, so new fuel injectors are recommended, nor does it cover labour or parts for engine installation/removal.

Frequently Asked Questions (FAQs)

Is carbon buildup a universal problem for all Audi S5 engines?

No, it's most prevalent in the early 4.2-litre V8 FSI engines (2008-2012) due to their direct injection design. The 3.0-litre supercharged V6 (2010-2017) can also experience it, but typically at higher mileages.

How often should I have the S-tronic transmission serviced?

Audi recommends servicing the S-tronic dual-clutch transmission with new fluid and a filter every 40,000 miles to help prevent premature failures, especially of the mechatronic unit.

Are coolant leaks always a sign of a major problem?

While often caused by common failures like cracked plastic water pumps or thermostat housings, any coolant leak should be addressed promptly to prevent engine overheating and more severe damage.

Does the Audi S5's timing chain always need replacing if there's a rattle?

A brief rattle on cold start (1-3 seconds) in 3.0-litre V6 models is often due to a worn tensioner, for which Audi issued a TSB. While not always indicative of imminent catastrophic failure, persistent or long-lasting rattles should be investigated by a specialist.

Is the rocker arm failure common on the B9 S5?

While it can lead to severe engine damage, it's important to note that rocker arm failure has affected only a very small percentage of early B9 S5 models (2018-2019). It is not considered a widespread issue.

What's the best way to maintain the S5's sound system?

For B9 Sportback models experiencing poor bass, checking and correcting the subwoofer's wiring phase is a common DIY fix. For rattling speakers, ensuring fasteners are tight or adding sound dampening can help, or upgrading to aftermarket speakers may be necessary.

Conclusion

The Audi S5 is undeniably a compelling machine, offering a fantastic blend of luxury, performance, and everyday usability. However, like many high-performance European vehicles, it comes with a set of known issues that prospective buyers and current owners should be aware of. From the notorious carbon buildup in earlier engines to the potential for transmission and suspension woes, understanding these common faults is key to a rewarding ownership experience. Regular maintenance, proactive checks, and a willingness to address issues promptly, ideally with an independent specialist, will ensure your S5 continues to deliver the thrilling drive and sophisticated comfort it's renowned for, rather than becoming a source of frustration. With the right knowledge, the Audi S5 can be a truly exceptional car to own and drive.

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