Audi A4 2.0 B6

The B6 A4 uses a sophisticated multilink front suspension with four control arms per side (eight total). Rubber bushings and ball joints wear over time, causing clunking over bumps, vague steering, and uneven tire wear. This is the single most common repair on the B6 chassis and is essentially inevitable on any example over 100,000 km. Individual arms cost 60-120 euros each for aftermarket parts, but most workshops recommend replacing the full set since one worn arm means others are close behind. A complete 12-piece front suspension kit costs 200-400 euros for quality aftermarket parts (Lemforder, Meyle HD) or 600-800 euros for OEM parts, plus 4-6 hours of labor. Wheel alignment (80-120 euros) is required after replacement. Nearly every B6 over 15 years old will have had this done at least once.

At 20+ years old, corrosion is the most visible issue on surviving B6 A4s. The rear wheel arches are the primary rust location, with paint bubbling at the lip caused by stone chips and the felt wheel arch liner rubbing against the painted surface. Front arches and the area around the rear license plate lights also rust due to water ingress. Sills develop corrosion where the stone-chip protection ends. Audi issued a special instruction for fender repair involving rust removal and additional sealing. Minor surface rust repair costs 200-400 euros per panel. Severe structural rust on sills can cost 800-1,500 euros and may make the car uneconomical to repair. Cars from Northern Europe and salt-road countries are most affected. Always check under the wheel arch liners during inspection.

The ALT engine is known for gradually increasing oil consumption as it ages, often consuming 0.5-1 litre every 4,000-5,000 km by the time it reaches higher mileages. The valve cover gasket is typically the first culprit, becoming brittle and allowing oil to seep out. Replacing the gasket costs 150-250 euros at an independent workshop. If oil consumption persists after gasket replacement, the valve stem seals are the likely cause. They harden with age and allow oil to leak past the valves into the combustion chamber, producing blue smoke on startup. Valve stem seal replacement costs 500-800 euros as the cylinder head must be partially disassembled. The PCV (crankcase ventilation) system should also be checked, as cracked ventilation hoses are common and can worsen oil consumption.

Ignition coil failure is one of the most common issues on the B6 A4 2.0 and across the entire B6 platform. Audi service departments have acknowledged expecting multiple coil replacements over the car's lifetime. Symptoms include rough idle, cylinder-specific misfire codes, hesitation under load, and a flashing check engine light. Individual coils cost 20-40 euros each. Replacing all four simultaneously along with new spark plugs is recommended, costing 100-300 euros total depending on whether OEM or quality aftermarket parts are used. The coils are easily accessible on top of the engine. Keeping a spare coil in the car is sensible advice, as failures can occur suddenly.

This issue only affects front-wheel-drive models with the Multitronic CVT automatic. Quattro models use a conventional Tiptronic, and manual gearboxes are trouble-free. The Multitronic is known for chain wear, transmission control module failures causing flashing PRND lights and limp mode, and friction plate burnout. Audi marketed the CVT fluid as a lifetime fill, but specialists strongly recommend changing it every 60,000 km with the correct G 052 180 A2 fluid. Diagnostic codes such as P0841, P0868, or P2714 indicate hydraulic problems requiring immediate attention. TCM repair costs 200-400 euros, but if the chain or clutch pack fails, a full rebuild runs 2,000-3,500 euros and a replacement gearbox can cost up to 4,500 euros. If buying a B6 A4 automatic, strongly prefer quattro with Tiptronic over FWD with Multitronic.

The wiring loom that passes through the rubber boot between the car body and the driver door flexes with every door opening. Over 20+ years, individual wires inside the loom fatigue and break. Symptoms appear progressively: central locking stops working on the driver door first, then the window stops responding, and eventually other door functions fail. The rubber boot can be pulled back to visually inspect the wires. Repair involves splicing the broken wires, which costs 100-200 euros at a workshop. A complete door loom replacement costs 200-400 euros including labor. This is extremely common on B6 A4s and is often the cause of intermittent central locking or window faults that owners attribute to other components.

The electric window regulators use plastic clips that become brittle with age and temperature cycling. When they break, the window drops into the door cavity or moves erratically. The driver side is most commonly affected due to heaviest use. Symptoms appear between 70,000-120,000 km and worsen in winter when frozen seals overload the motor. Replacement regulators cost 40-80 euros for aftermarket parts plus 1-2 hours of labor. Aftermarket metal-clip upgrades are available and more durable than the original plastic design. Expect to replace at least one regulator on any B6 over 15 years old.

The ALT engine uses plastic coolant flanges and a plastic thermostat housing that become brittle after years of heat cycling. Symptoms include slow coolant loss, white residue around hose connections, or overheating if the thermostat sticks closed. The parts are cheap (30-60 euros) but incorrect refilling can trap air pockets. An upgraded aluminum replacement flange is available for around 50 euros and provides a permanent fix. Total repair including labor runs 150-400 euros. The water pump should be inspected at the same time if not recently replaced.