Audi A4 B8 (2007-2015) Common Problems: What to Check Before You Buy

The B8 A4 - saloon, Avant and allroad, sold from 2007 until around 2015, with a facelift usually called the B8.5 arriving around 2012 depending on market - is a well-built, comfortable car that generally ages tidily, but it has a short list of characteristic faults worth knowing before you buy one or spend money on the one you own. Almost all of them are engine-specific or year-specific, so the useful question is never 'is the B8 reliable' but 'which B8 is this'. The headline items are timing chain tensioner wear and oil consumption on the four-cylinder TFSI petrols, DPF, EGR and intake flap trouble on the diesels, the Multitronic CVT fitted to front-wheel-drive automatics, and water getting into the cabin through blocked drains and taking the electrics with it. Front suspension bushes, the steering - hydraulic on earlier cars, electromechanical after the facelift - and the electronic parking brake are the other regulars. None of that makes the B8 a bad car. It makes it a car you check properly rather than assume about.

Timing chains, belts and the noise you can hear from the driver's seat

Which engine you are looking at changes this completely, so get it straight before anything else. The four-cylinder 1.8 and 2.0 TFSI petrols are turbocharged and run a timing chain, driven from the gearbox end of the engine. The four-cylinder 2.0 TDI is a common-rail diesel driven by a toothed cambelt - a scheduled service item, and one you must not let slide, because a snapped belt means valves meeting pistons. Everything above those runs chains: the naturally aspirated 3.2 FSI V6 petrol on early cars, the 2.7 and 3.0 V6 TDI diesels, the 3.0 TFSI V6 in the S4, which is supercharged rather than turbocharged, and the naturally aspirated 4.2 V8 in the RS4, which in this generation was built as an Avant only. On those engines the chains sit at the flywheel end, so chain work means the engine or gearbox comes out. The chains themselves often last; the labour bill if they don't is why people are wary.

On the four-cylinder TFSIs the recognised weak point is the chain tensioner rather than the chain, and it is the earlier design that has the reputation. As the tensioner wears you get a rattle for a second or two on a cold start, sometimes only after the car has stood overnight or been parked nose-down, fading as oil pressure comes up. Revised tensioner parts exist and the repair is well understood, but it is not a small job either - that chain is at the gearbox end of this engine too - and if a chain skips a tooth the engine can be wrecked in an instant. Treat a cold-start rattle as a stop-and-investigate item, not a quirk, and pay more for a car with receipts showing the work has been done.

One safety note that applies to every engine here: a red oil pressure warning means stop and switch off, not finish the journey. By the time that light is on, damage is already being done - and on a chain-driven engine, low oil pressure is also exactly what starves a hydraulic chain tensioner. Regular oil changes to the correct specification are not optional maintenance on these engines; they are part of what keeps the timing drive alive.

• Start the car from stone cold yourself, engine off overnight if you can, and listen to the first few seconds
• On a 1.8 or 2.0 TFSI, ask directly whether the chain tensioner has been replaced and ask to see the invoice
• On a 2.0 TDI, check the cambelt history - it is normally done with the water pump, tensioner and rollers
• On V6 and V8 cars, understand that chain access means engine or gearbox out before you need to find that out
• Look for a consistent oil change history with the right oil spec, not just stamps
• Any oil pressure warning: stop, do not drive it home

Oil consumption, breathers and coolant leaks on the TFSI petrols

Oil use is the best-known four-cylinder TFSI complaint on this generation. Earlier engines in particular can get through noticeable amounts between services, from a combination of piston ring and oil control design and a crankcase breather system that lets oil into the intake. It shows as regular top-ups, a puff of smoke on start-up or overrun, oily deposits in the intake pipework and fouled spark plugs. Remedies range from a new breather to stripping the engine for pistons and rings, so it matters enormously which end of that scale a given car is at. Consumption varies a lot between individual cars, so check the dipstick before and after the test drive and ask the owner point blank how often they top up rather than judging by model year.

The crankcase breather, or PCV, is a common failure in its own right. When its diaphragm splits you get a hissing or whistling noise, a lumpy idle, sometimes oil pushed past crank seals or the dipstick tube, and lean or high-idle fault codes. It is a routine job and worth ruling out before anyone starts talking about pistons.

Two more to look for on the petrols. The plastic water pump and thermostat housing module leaks with age - look for coolant loss, low coolant warnings and dried crusty residue around the front of the engine. And because these are direct-injection engines, carbon builds up on the intake valves over time, causing rough cold running, misfires and a general lack of sparkle; the fix is manual cleaning, usually walnut blasting. The later, revised versions of this engine family, which added port injection alongside direct injection, are generally reckoned to be better on both counts - but not every facelift car has one, so judge the car in front of you on its evidence rather than its year. The turbo diverter valve is also a known failure item, showing up as lost boost and an underboost code.

The diesels: DPF, EGR and intake flaps

The B8's four-cylinder diesel is a common-rail 2.0 TDI - the older pump-duse units belong to the previous car - and there are 2.7 and 3.0 V6 diesels above it, the 2.7 being an earlier-car engine. All of them are happiest on long runs. A short-journey life is what causes most of the trouble, because the diesel particulate filter never gets hot enough to complete a regeneration. That shows as a DPF warning, reduced power or limp mode, and an oil level that creeps up on the dipstick as unburnt diesel dilutes the oil. Ask whether the DPF has ever been replaced or cleaned, and be aware that a removed DPF is an MOT failure and illegal on a UK road car.

The EGR valve and cooler soot up and stick, giving poor running, an engine light and occasionally coolant loss if the cooler itself fails. The intake manifold flaps are a genuine B8-era signature fault: on the 2.0 TDI the flap actuator or its linkage fails and throws the classic manifold runner code, while the V6 diesels have swirl flaps in manifolds that gradually pack with oily soot. On higher-mileage cars the manifold is often replaced rather than cleaned.

Injectors are the other diesel item worth listening for - a hard knock or rattle from one cylinder, uneven running, smoke, or a soot ring and a chuffing noise around the base of an injector where the seal has failed. Glow plugs give hard cold starts and a winter engine light, and can seize in the head. Finally, many 2.0 TDIs of this era were covered by the emissions service action; check the service history to see whether it has been carried out on the car you are looking at.

Gearboxes: Multitronic, S tronic and the quattro automatics

Front-wheel-drive automatics generally used the Multitronic CVT, and it is the transmission people worry about most. Typical symptoms are a judder or shunt as you pull away from rest, a hesitation before drive engages, slipping under load, or a sudden drop into limp mode. Fluid condition matters a great deal and many were never serviced because owners assumed sealed for life. A well-maintained one can be fine; an unknown one is a risk you should price in. Always test it from cold and from a genuine standstill, not just rolling. Note that the CVT was phased out towards the end of the car's life, so a late front-drive automatic may be a dual-clutch instead - check what is actually fitted rather than assuming from the driven wheels.

Quattro automatics used a conventional torque-converter automatic - a six-speed on earlier cars, an eight-speed on later ones - and these are usually the tougher choice. They still want a fluid and filter service. Some models, including the S4 and the RS4 Avant, used the seven-speed S tronic dual-clutch instead; there the wear points are the mechatronic unit and the clutch pack, felt as hesitation, shunting or juddering at crawling speed and in car parks. Its fluid and filter service is not optional.

Manuals are straightforward. Listen for dual-mass flywheel rattle at idle that disappears when you press the clutch, and feel for a juddering take-up. One useful thing to know: quattro on the B8 is a mechanical centre differential, not the Haldex clutch used in transverse VW Group cars, so there is no Haldex pump or filter to service here - just gearbox and final drive oils. A vibration that appears at motorway speed can be the propshaft centre support bearing.

Steering, parking brake and suspension

Steering depends on which side of the facelift the car sits. Earlier B8s use a conventional hydraulic rack driven by an engine-mounted pump, so the things to look for are fluid level and leaks, dampness around the rack and lines, and whining or heaviness at parking speeds. The 2012 facelift moved most models to electromechanical power steering, with no pump or fluid to check; when that faults you normally get a steering warning on the dash and noticeably heavier steering. Either way the car remains steerable - the assistance goes, not the connection - but the effort goes up a lot, especially when parking, so treat any steering warning, even an intermittent one that clears on restart, as something to get diagnosed before you keep using the car.

The electronic parking brake is a common annoyance across the range. The motors on the rear calipers seize with age and corrosion, and the system will also throw a fault if rear pads have been changed without putting it into service mode first. Corroded connectors and wiring at the back of the car can produce the same warning without anything mechanical being wrong. Symptoms are a parking brake warning, a brake that will not release, or one rear wheel binding and a hot wheel after a drive. On cars that do gentle mileage the rear discs corrode at the edges too.

The front suspension is a multi-link design with a lot of arms, and the bushes and ball joints in them are a well-known wear item on this platform. You will hear knocking over speed bumps and broken surfaces, feel vagueness or wander on the motorway, and see wear on the inner edges of the front tyres. Arms are usually replaced in sets and the car needs a proper four-wheel alignment afterwards - skipping that is how people end up buying tyres twice. Anti-roll bar drop links rattle over small bumps and are cheap. On xenon cars, check the headlight self-levelling sensor linkage down by the suspension arm; they snap and give beam aim faults.

Water ingress and the electrical gremlins it causes

If a B8 develops strange, unrelated-looking electrical faults, look for water before you look at wiring. The drains in the plenum area under the scuttle fill with leaves and silt, and once that chamber holds water it finds a way in - past the pollen filter housing, along the bonnet release cable grommet, or through the large wiring connector cover. Door membranes lift and let water past, and on sunroof cars the roof drains block and run down an A-pillar. The water collects under the carpet or underlay where you cannot see it, and the carpet often feels dry on top.

Once the footwells are damp, control modules and connectors low in the car start corroding. That produces exactly the kind of fault that drives owners mad: central locking that works sometimes, windows that stop one-touch, warning lights that come and go, an alarm that triggers on its own, and a battery that goes flat when the car sits for a few days. Chasing those symptoms electrically without finding and fixing the leak is money thrown away, and a soaked module is not a cheap thing to replace.

Two related things. Check the boot floor and spare wheel well for standing water or a tide mark, which usually points at rear light or boot seals. And if a battery has been replaced, it should be registered and coded to the car's energy management system - if it was not, the charging strategy is wrong for it and the battery tends to die early. Elsewhere in the cabin, expect the usual for the era: door lock micro-switches giving false door-open warnings, peeling soft-touch coating on some switches and trim, and worn driver's seat bolsters. Cosmetic, but they tell you how the car has lived.

What to check on a test drive or pre-purchase inspection

Arrange to see the car completely cold. A seller who has warmed it up before you arrive has hidden the single most useful test on this model. Give yourself half an hour before you drive anywhere, and take a torch.

The drive itself should include a standstill start, some slow crawling, a rough road at low speed and a decent stretch at motorway pace. Most B8 faults will announce themselves in that mix.

• Cold start: listen for a chain rattle on a TFSI, injector knock or excessive smoke on a diesel
• Idle: hissing or whistling from the breather, lumpy running, misfires
• Check the oil level and its condition, and ask how often it is topped up
• Check the coolant header tank level and look for dried residue around the pump and thermostat area
• On an earlier car, check the power steering fluid and look for leaks at the rack and hoses; on a facelift car, check the steering warning behaves on ignition
• Multitronic: pull away from a full stop several times from cold, feel for judder, hesitation or slipping
• S tronic: crawl in traffic and do a few reverse manoeuvres, where clutch and mechatronic wear shows first
• Suspension: low-speed rough road with the radio off, and inspect the inner edges of the front tyres
• Parking brake: apply and release it several times, listen for both motors, feel the rear wheels for heat after the drive
• Warning lights: confirm they all illuminate on ignition and then go out - especially airbag, ABS and steering
• Lift the carpets in all four footwells and the boot floor, and press the underlay with your hand
• Service history: cambelt on a 2.0 TDI, DPF history, gearbox fluid changes, any chain tensioner work
• Ask an Audi dealer to check the VIN for outstanding recalls and service actions, including the airbag inflator campaigns that affected a wide range of cars of this era
• Scan every module before you commit, not just the engine

Fault codes that turn up on the B8, and what they actually point at

Be clear about what a stored code is: it names a circuit, a plausibility check or a symptom the engine management noticed, not the broken part. On this generation the same code routinely has three or four possible causes, and a couple of the important ones are caused by something as mundane as a tired battery or a wet module. Read the code, then prove the cause with live data before anyone spends money.

Some that come up often on the B8 and what they usually mean in practice. Camshaft and crankshaft correlation codes such as P0016, P0011 and P0017 on a four-cylinder TFSI should never be waved away - they can be a cam adjuster or its solenoid, or low oil pressure, but they are also exactly what a stretched chain or a failing tensioner produces. P2015 on a 2.0 TDI is the intake manifold flap, usually a broken linkage or actuator. P0299 underboost on a diesel is typically sticking turbo vanes, a split hose or a boost leak. P0401 and P0402 point at EGR flow, and DPF codes such as P2002 or P242F at a filter that has not been regenerating. P0087, low fuel rail pressure, deserves respect on a common-rail diesel - filter, supply or pump, and worth stopping for. On the petrols, P0171 lean running and a high idle code very often trace back to the breather diaphragm or an intake leak, and P0128 is the thermostat. Misfire codes are usually coils and plugs, but on a direct-injection engine, carbon and injectors are the next suspects.

Alongside the standard P-codes, the comfort, convenience and chassis modules report VAG's own five-digit codes, and those are where the water ingress story usually shows up as a scatter of implausible-signal faults across unrelated modules. That is the case for reading everything rather than just the engine. VAGPULSE, the Windows software and cable sold on this site, is built for that job: one payment, a full scan of every module in the car, live measuring blocks so you can watch actual against specified boost or rail pressure while the fault is happening, plus the coding and adaptation side - putting the electronic parking brake into service mode, registering a new battery, resetting throttle and steering angle adaptations. Whatever you use, read all modules and check freeze-frame data before replacing a single part.

Common questions