Why does my Audi or Volkswagen leak oil everywhere? Most likely, there is a blockage in the breather hose and/or failure of the engine crankcase breather valve. How does the oil breather vent system work on a Volkswagen? As the oil heats up in the crankcase, vapor is produced and needs to be vented. It travels up that tubing to the pressure regulating valve (crankcase breather valve). Due to emissions regulations, this vapor must be routed back to the intake side of the engine to be added to the incoming air and burnt off. This leads to the two most common problems. If there is a blockage, pressure builds up in the crankcase and causes oil to push out and leak from the weakest parts (seals and gaskets) of the engine.
The second part to the leak problem comes from when the car is shut off. The oil is still hot, giving off vapor, which is routed into the intake tube. Now the vapor is just sitting there since the engine is off, the vapor cools, condenses back to a liquid and leaves an oily mess behind.