Crankcase Vent System, Valves & Hoses
The BMW crankcase vent system separates liquid oil from the air inside the engine and intake. When working correctly, oil is removed from the intake air and returned to the oil pan. Oil vapor remains and is burned up in the combustion chamber. Every car has some form of crankcase ventilation, also known as a PCV, CCV, oil separator, and a cyclonic separator. BMW CCV system are notoriously failure prone, leading to high oil consumption, burning oil, loss of power, misfiring, and high carbon deposits. The problems are worse on the turbocharged models where the CCV needs to keep up with the pressure from the turbocharger(s). An overhaul of the CCV system should be planned every couple of years and especially before the winter months. Signs of a failing CCV include: whistling noises in the intake, blueish smoke in the exhaust, high oil consumption, and thick white or yellow gunk under the oil cap.