Audi A4
Naturally aspirated engine with 5-valve technology and 92 kW. Rev-happy and refined, though elevated oil consumption possible from approx. 150,000 km. Timing belt change is critical.
Solid everyday engine — gets the job done
125 hp 1.8L for daily use. Watch the known weak points. Manual gearbox is pleasantly light.
Engine Weaknesses 6
The fuel pump relay (part no. 167) under the steering column is a known failure point on the AGN 8L. A dead relay creates multiple seemingly unrelated faults (injectors, camshaft) because the fuel pump doesn't run.
Symptoms: Engine refuses to start after a long stand; restart possible after a short wait; multiple fault codes with no obvious common cause
The camshaft position sensor on the AGN can fail, causing sporadic misfires and fault codes. Often triggered by moisture ingress after an engine wash.
Symptoms: Camshaft position fault code, engine running on three cylinders, sporadic misfires.
Hydraulic tappets on the 1.8 20V rattle on cold start due to delayed oil supply. Often caused by blocked oil feed jets or oil pump wear. The noise typically disappears once the engine warms up.
Symptoms: Loud ticking or tapping on cold start that fades after 1–2 minutes of running; noise persists if the oil pump is faulty
Ignition coils on the 1.8 20V are known wear items. Failure is typically caused by electrical breakdown or moisture ingress. A dead cylinder can damage the catalytic converter through unburnt fuel.
Symptoms: Juddering and power loss especially in cold and wet conditions; engine running on three cylinders (felt as vibration); misfire codes (P030x); improvement when warm
The AGN uses a cam phaser (VANOS). The solenoid valve that controls it wears out or gets clogged with oil deposits. Cam timing fault codes appear without any noticeable driveability issue.
Symptoms: Engine warning light, slight power loss in the lower rev range, occasional load judder
The electronically controlled throttle body on the AGN must be re-adapted after every cleaning. Skip this step and you get idle problems and stalling at traffic lights.
Symptoms: Rough idle, engine stalls at junctions, fluctuating rpm at standstill.
Vehicle Weaknesses 5
Despite a fully galvanised body, the A4 B5 rusts at typical spots: door lower edges (behind door strips), bonnet fold at the sides, boot lid, lock panel and roof folds. Rust in roof rails is a well-known long-term issue on many A4 B5s.
The lower straight control arms and their rubber bushings are worn out on almost all older A4 B5s. Characteristic squeaking and knocking noises over bumps. Replacement parts are available cheaply (Lemförder ~€35 each).
Rust-like particles in the A4 B5 coolant reservoir indicate a clogging heater core. The symptom is poor heating performance. At higher mileages, old coolant hoses and the heater core itself must be inspected.
The A4 B5 AC compressor shows first signs of weakness from as little as 60,000 km. Common symptoms are loud noises when the AC is switched on or complete cooling failure. Quality replacement compressors are available.
With increasing age the A4 B5 frequently experiences window regulator motor failure, door lock motor failure, mirror adjustment motor failure and immobiliser transponder failure. These wear issues are typical for a 25+ year old vehicle.