Rear timing chain tensioners fail (rattling noise at startup). Repair is engine-out – very expensive. All engines: Timing belt + water pump must be replaced every 60–75k miles . Failure destroys valves. Tip: Buy a kit (ContiTech or Gates) with a metal-impeller water pump.
The B6 offered three transmissions, but they are not created equal. audi a4 b6 common problems
This is the number one killer of the B6 1.8T. Due to a combination of a small oil capacity, a hot-running turbo, and long factory service intervals (10,000 miles), the oil would cook and block the oil pickup tube in the oil pan. Rear timing chain tensioners fail (rattling noise at