The flagship diesel in the D4-generation A8, the 4.2 V8 TDI paired twin Garrett turbochargers with a four-litre-plus displacement to produce 350 hp (pre-facelift) or 385 hp (post-2013 facelift). Mated to a ZF 8-speed automatic and permanent quattro, it offered effortless performance in an aluminium-bodied luxury sedan weighing over two tonnes. Heavy depreciation makes these available for a fraction of the original price, but V8 diesel complexity and flagship-level electronics keep running costs firmly in premium territory.· more· less
Powerful, torquey V8 dieselAluminium body resists corrosion
Twin turbo V8 repair complexityAir suspension repairs are costly
Buy if: You want a powerful diesel luxury cruiser for long-distance use and can find one with full Audi service history and healthy air suspension.
Avoid if: You mainly drive short urban trips, need predictable running costs, or the car shows any sign of cold-start rattle or suspension sag.
Rear-mounted timing chains stretch over time, causing cold-start rattle and potential valve damage · more· less
The 4.2 V8 TDI uses single-row timing chains mounted at the rear of the engine, making replacement a major undertaking that often requires engine removal. Symptoms begin with a metallic rattle on cold start as the tensioners lose hydraulic pressure overnight and cannot take up chain slack. Typically occurs between 120,000 and 200,000 km. If ignored, the chain can skip teeth, causing catastrophic valve-to-piston contact. Parts cost €600-1,400 for chains, tensioners, and guides. Labour runs €2,000-3,500 due to the 20-35 hours required, including engine removal and reinstallation. Specialists recommend replacing all chains, tensioners, and guide rails as a set to avoid repeat work.
Air suspension strut failure
up to €3,0002 of 8
Air springs leak over time, causing the car to sag overnight or sit unevenly · more· less
The adaptive air suspension is standard on all A8 D4 models. Air springs typically begin leaking between 80,000 and 150,000 km due to rubber membrane degradation. Symptoms include the car sitting lower on one corner after standing overnight, or the compressor running excessively on start-up. An OEM air strut costs approximately €1,200-1,500 per corner from Audi, though quality aftermarket replacements from Arnott or Bilstein are available for €300-550 each. If a leaking spring is ignored, the compressor overworks and burns out, adding another €500-800 for replacement. The electronic level sensors (€100-200 each) and valve block (€300-500) can also fail. Budget €800-1,500 per strut including labour at an independent shop, or up to €2,500-3,000 per corner at an Audi dealer.
DPF clogging from short-trip driving
up to €2,5003 of 8
Diesel particulate filter blocks up if the car rarely reaches sustained motorway speeds · more· less
The DPF requires periodic regeneration at sustained speeds of 60+ km/h for 15-20 minutes. Urban-only driving prevents passive regeneration, leading to excessive soot accumulation. Symptoms include a DPF warning light, reduced power, and increased fuel consumption. Professional DPF cleaning costs €300-500 and can resolve moderate blockage. Severe cases requiring DPF replacement run €1,500-2,500 including labour. Failed regeneration can also stem from faulty differential pressure sensors (€150-250 to replace). Facelift models (2013+) with improved exhaust gas management experience this less frequently. The twin-turbo V8 generates less soot than smaller TDI engines, making this less common than on 2.0 or 3.0 TDI models, but the issue remains relevant for cars used predominantly in city traffic.
EGR valve and cooler clogging
up to €1,5004 of 8
Carbon deposits accumulate in the EGR system, causing rough running and warning lights · more· less
The exhaust gas recirculation system on the V8 TDI is prone to carbon buildup, particularly with frequent short trips and low-speed urban driving. Symptoms include rough idle, reduced power, and a check engine light. Cleaning the EGR valve is possible at €200-400, but replacement costs €600-1,200 including labour due to the V8's packaging making access difficult. The EGR cooler can also crack or leak, which is more expensive to address (€800-1,500). Cars with regular motorway use and timely oil changes are less susceptible. Typically becomes an issue between 80,000 and 150,000 km depending on driving pattern.
Turbo actuator sticking or turbo wear
up to €4,0005 of 8
Electronic turbo actuators stick or internal turbo bearings wear due to oil supply issues · more· less
The twin Garrett turbochargers are variable-turbine-geometry units, and their electric VTG actuators and vanes can stick from carbon buildup, particularly on cars driven gently at low boost. Symptoms include loss of power, limp mode, and EPC warning light. An actuator replacement costs €400-600 per side including labour. More seriously, turbo bearing wear from oil degradation or restricted oil supply lines can necessitate turbo replacement at €1,500-2,000 per turbocharger including labour. The V8 TDI uses two turbochargers (one per bank), so costs double if both need attention. Regular oil changes with VW 507.00 specification oil and occasional spirited driving help prevent actuator sticking. Most issues appear between 100,000 and 180,000 km.
AdBlue system and NOx sensor failure
up to €1,5006 of 8
AdBlue injector crystallizes or NOx sensors fail, triggering emissions warnings and start counters · more· less
Post-2014 facelift models use SCR (Selective Catalytic Reduction) with AdBlue injection for NOx reduction. The AdBlue injector can crystallize in the exhaust pipe, and NOx sensors degrade over time. A failed NOx sensor costs €200-400 per unit, while AdBlue injector replacement runs €400-700 including cleaning. In severe cases, the SCR catalyst itself may need replacement at €1,000-1,500. The system may trigger a countdown warning limiting engine starts if faults are not addressed. Pre-facelift models (2010-2013) use a different emissions strategy and are generally less affected by AdBlue-specific issues.
Electrical and MMI system faults
up to €1,5007 of 8
Retractable MMI screen, control modules, and comfort electronics develop intermittent faults · more· less
The D4 A8 has extensive electronic systems including the retractable MMI display, which is operated by the rotary controller and a separate handwriting-recognition touchpad rather than being a touchscreen, plus adaptive cruise control, keyless entry, and numerous comfort modules. Common issues include the MMI screen failing to extend or retract properly, screen display going blank intermittently, climate control malfunctions, and parking sensor false alerts. An MMI screen mechanism repair costs €300-500. A defective MMI control module replacement runs €350-700. Individual comfort module failures (seat control, door module, sunroof drain sensor) typically cost €200-500 each. Software updates from Audi can resolve some intermittent issues. The complexity of networked electronics means that a single failed module can trigger cascading warnings across multiple systems.
Coolant control valve leak (2010-2013)
up to €1,2008 of 8
Coolant switching valve leaks on early cars, potentially allowing coolant into engine control module · more· less
Certain 2010-2013 A8 models were subject to a recall for a coolant valve that could leak, allowing coolant to reach the engine control module. If the ECU is damaged, replacement costs escalate significantly to €800-1,200 including programming. The valve itself is a relatively inexpensive part (€100-200), but the labour and potential ECU damage make this a costly repair if missed. The matching Audi campaign 80B9 was issued for US 2011-2012 and Canadian 2010-2012 A8s, so ask the dealer to confirm against the VIN whether a European action applies to this car. Post-2013 facelift models are not affected.
Robust engine in a complex package
The 4.2 V8 TDI is widely regarded as a strong engine, with many examples exceeding 200,000 km without major powertrain issues when properly serviced. However, the combination of twin turbochargers, rear-mounted timing chains, air suspension, and flagship-level electronics means that when repairs are needed, they tend to be expensive due to parts costs and labour intensity. Cars used for regular motorway driving with full service history age significantly better than those used for short urban trips. Budget for air suspension work as a near-certainty on higher-mileage examples.
Service history
Complete Audi dealer or specialist records essential. Verify oil changes every 15,000 km or annually with VW 507.00 specification oil.
Tires
Check tread depth, age, and uneven wear patterns. 265/40 R20 tires are expensive to replace.
Cold start
Start engine completely cold. Listen for timing chain rattle in the first 10-30 seconds.
Test drive
Minimum 30 minutes including motorway speeds to reach full operating temperature and allow DPF regeneration.
Specific for this vehicle
Check air suspension ride height on all four corners
With the car parked on level ground, check that all corners sit at the same height. Lower the car to its lowest setting and raise to highest. Each corner should respond evenly. Listen for the compressor running after the car has been standing overnight.
Listen for timing chain rattle on cold start
The engine must be completely cold (sitting overnight). A metallic rattle in the first 5-30 seconds indicates chain tensioner wear. Brief rattle under 2 seconds can be acceptable, but sustained rattle is a warning sign of expensive repair ahead.
Check for DPF and AdBlue warning lights
Drive for at least 20 minutes and watch for DPF regeneration warnings or AdBlue system alerts. Check if the DPF warning light illuminates during city driving. Ask the seller about DPF regeneration frequency.
+ 4 more checksShow less
Test turbo response under acceleration
Accelerate firmly from low rpm in 3rd or 4th gear. Both turbos should spool smoothly without hesitation, smoke, or warning lights. Any sudden loss of power or EPC light suggests turbo actuator or boost leak issues.
Test MMI screen and all electronics
Operate the retractable MMI display multiple times and test the MMI touch handwriting pad. Test all climate zones, seat heating, ventilation, and massage functions. Check for warning lights on the dashboard and use a diagnostic scan for stored fault codes.
Verify coolant valve recall completion (2010-2013 models)
For pre-facelift cars built 2010-2013, confirm the coolant valve recall has been completed. Contact Audi with the VIN to verify.
Inspect underbody for oil leaks
Check the engine bay and underbody for oil seepage around valve covers, turbo oil lines, and oil pan gasket. Minor seepage is common on V8 diesels with high mileage, but active dripping indicates repairs needed.
Recalls and Technical Service Bulletins
Coolant control valve leak into engine control module - the matching Audi campaign 80B9 covers US 2011-2012 and Canadian 2010-2012 A8s, so European applicability is decided by VINVerify applicability with the VIN
Standard glass sunroof may break unexpectedly - European campaign 60B6 (A8 built March - July 2013)Critical - verify completed
Takata airbag inflator (selected production dates, check by VIN)Verify if applicable
Contact Audi with the VIN to verify all recalls have been completed. Campaign 60B6 for the standard glass sunroof covers cars built between March and July 2013 and reaches pre-facelift 4.2 TDI examples, so it is the one to check first. The coolant valve campaign 80B9 was issued for North America, and whether a European action applies to a given car is decided by the VIN. The Dieselgate-related emissions recall involves a software update for EGR thermal windows ordered by the KBA.
Warranty Status
Factory warranty (2 years)Expired on all used A8 D4 models
Rust perforation warranty (12 years)May still apply on 2014+ models
Extended warrantyAvailable through Audi dealers, typically €1,500-2,500/year
All A8 D4 models are well outside their original 2-year factory warranty. An extended warranty is strongly recommended given the potential for expensive air suspension and electronic repairs. Verify coverage terms carefully, as air suspension components are often excluded or subject to wear-and-tear clauses.
Sources: Research draws on model-specific owner forums and owner communities, recall information from official authorities, German automotive press, and multiple workshop cost references cross-checked against each other.
This report is for informational purposes only and does not constitute professional advice. Estimates may be inaccurate. Always have a qualified specialist inspect the vehicle before purchase. We accept no liability for decisions made based on this information.
