The B7 A4 with the 2.0 TDI was one of the best-selling diesel mid-size sedans in Europe during the mid-2000s, offering good motorway refinement and strong fuel economy. Engine codes include BLB/BNA (140 hp, early), BPW (140 hp, later), and BRE/BRD (140-170 hp with piezo injectors). All variants share the Pumpe Duse (PD) injection system. The car is well-built and comfortable, but one critical design flaw overshadows everything: the balance shaft/oil pump hex drive problem that can destroy the engine without warning.
Good fuel economy, strong torque
Solid build, refined highway cruiser
Balance shaft can destroy engine
Multitronic CVT unreliable (if equipped)
Buy if: You find one with a manual gearbox, verified balance shaft upgrade, and complete service history showing regular oil changes.
Avoid if: You cannot verify the oil pump hex shaft status, or the car has a Multitronic CVT gearbox with no documented fluid changes.
Expected Annual Maintenance Costs
Common Problems
Undersized hexagonal drive shaft between balance shaft and oil pump rounds off, causing sudden oil pressure loss · more· less
This is the most critical issue with the B7 2.0 TDI. The oil pump is driven by a hexagonal shaft connected to the balance shaft module. The hex engagement depth was only 4mm — insufficient for the torsional forces involved. Over time, the hex rounds off, reducing oil pump output. When it fails completely, oil pressure drops to zero and the engine can seize within seconds. Affected engine codes include BLB, BNA, BRE, BRD, and BPW — essentially all 2.0 TDI PD engines used in the B7 A4 up to approximately 2007. Failure typically occurs between 100,000-160,000 km. Early symptoms include brief metallic rattling at startup or idle, and low oil pressure warnings. A preventive upgrade to the revised spur-gear-driven system costs approximately €1,200-1,700 including parts and labor. If the engine has already sustained damage from oil starvation, a replacement engine or rebuild runs €3,000-5,000. Some specialists offer hex shaft restoration for around €300-400 plus labor, though the full spur gear conversion is the preferred permanent fix.
Turbo bearing wear or VNT vane sticking, often accelerated by the oil pump issue · more· less
The Garrett turbocharger on the 2.0 TDI has a typical lifespan of 150,000-200,000 km with proper maintenance. Failure modes include bearing wear (caused by oil starvation — often linked to the hex shaft issue), VNT vane sticking from carbon deposits, and wastegate actuator failure. Symptoms include blue or black exhaust smoke, whistling noises, power loss, and limp mode. If the oil pump hex shaft has been failing gradually, reduced oil supply accelerates turbo wear. A reconditioned turbo costs €500-700; a new unit runs €700-1,000. Labor is approximately 3-4 hours at €80-120/hour. If VNT vanes are merely stuck from carbon, cleaning can resolve the issue for €200-400. Regular motorway driving and timely oil changes are the best prevention.
Early Siemens piezo injectors short-circuit internally, shutting down the engine without warning · more· less
The 170 hp variants (BRD and BRE engine codes) use Siemens piezo injectors that operate at approximately 150V. The insulation on early injectors breaks down, causing a short to ground that immediately shuts down all injectors as a protective measure for the ECU. The engine cuts out without warning — a safety concern if it happens at speed. Audi issued a recall: affected injectors have part numbers ending in 'M', and the fix involves replacing all four injectors and the injector wiring harness. Verify recall completion via VIN check. If the recall was missed, replacement of all four injectors costs €800-1,500 for aftermarket parts or €1,500-2,500 with OEM Siemens units plus labor. The 140 hp BPW/BLB engines use different injectors and are not affected by this specific issue.
Diesel particulate filter clogs from short-trip driving, causing power loss and warning lights · more· less
Models from 2006 onwards were fitted with a DPF as standard. The filter regenerates by burning off accumulated soot during sustained driving at higher temperatures. Short-trip and urban-only driving prevents regeneration, leading to progressive clogging. Symptoms include reduced power, increased fuel consumption, and a DPF warning light. Early-stage clogging can sometimes be resolved with a forced regeneration via VCDS (€50-100 at a workshop). Professional DPF cleaning costs €200-400. If the filter is ash-saturated beyond cleaning, replacement costs €600-1,200 for an aftermarket unit or €1,200-2,000 for OEM, plus approximately 2-3 hours labor. Earlier BLB/BPW models without DPF avoid this issue entirely, which is one reason they remain popular.
Chain-driven CVT develops judder, slip, and control unit faults, especially with neglected fluid changes · more· less
Front-wheel-drive B7 A4s were available with the Multitronic CVT transmission. Despite Audi calling the transmission fluid a lifetime fill, this is widely disputed by specialists who recommend fluid changes every 40,000 km. Neglected fluid leads to metal particle contamination, clogged solenoids, and chain/pulley wear. Common symptoms include juddering from standstill (especially when cold), hesitation, and PRND flashing on the dashboard. Failure typically occurs between 120,000-200,000 km. A control unit repair costs approximately €500-1,000. A full rebuild at a specialist runs €2,000-3,500. Complete transmission replacement can reach €4,000-5,000. Cars with a manual 6-speed gearbox are significantly more reliable. Quattro models use a conventional Tiptronic automatic which is generally more durable.
Multilink front suspension bushings and ball joints wear out, causing clunking and vague steering · more· less
The B7 A4 uses the same sophisticated multilink front suspension as the B6, with four control arms per side (eight total). Rubber bushings and ball joints deteriorate over time, particularly on rough roads. Symptoms include clunking over bumps, imprecise steering feel, and uneven tire wear. This is essentially inevitable on any B7 A4 over 100,000-120,000 km. A complete 8-arm kit with ball joints costs €200-400 for quality aftermarket parts (Meyle HD, Lemforder) or €600-800 for OEM. Labor is 4-6 hours plus a mandatory alignment (€80-120). Replacing individual arms is possible but most specialists recommend the full kit since one worn arm indicates the rest are close behind.
Carbon and soot deposits restrict EGR valve and intake manifold flaps, causing rough idle and power loss · more· less
The EGR valve recirculates exhaust gases into the intake, and carbon deposits gradually restrict flow. This is worse with short-trip driving. Symptoms include rough idle, hesitation, increased fuel consumption, and the engine management light. The intake manifold flap mechanism can also seize from carbon buildup. Cleaning the EGR at a workshop costs €100-200. Replacement of the EGR valve costs €200-400 for parts plus 2-3 hours labor. If the intake manifold flap actuator also needs attention, add €100-200. Many owners in countries where it is permitted choose to blank off the EGR, which permanently prevents recurrence.
Balance shaft issue dominates the risk profile
The 2.0 TDI PD engine in the B7 A4 can be a solid long-distance diesel when the balance shaft/oil pump hex drive has been upgraded to the revised spur gear design. Without this upgrade, the engine is at significant risk of sudden, catastrophic failure between 100,000-160,000 km. Manual gearbox cars with a confirmed hex shaft upgrade and regular servicing are the most dependable choice. Multitronic CVT-equipped cars add another major expense risk. Verify both the hex shaft status and gearbox service history before committing to purchase.
Recalls and Technical Service Bulletins
Siemens piezo injector failure (2005-2007 BRD/BRE 170 hp variants)
Verify completed
Takata airbag inflator (2004-2008 models)
Verify completed
Contact an Audi dealer with the VIN to verify all recalls have been completed. The piezo injector recall is particularly critical for 170 hp models — engine shutdown at speed is a safety concern.
Warranty Status
Factory warranty (2 years)
Expired on all B7 A4s
Rust perforation warranty (12 years)
Expired on all B7 A4s
All Audi A4 B7 models are well outside their original 2-year factory warranty and 12-year rust perforation warranty. Extended warranty options for cars this old are extremely limited and typically exclude pre-existing conditions.
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.