1994-2007 BMW Engines Crankcase Ventilation System Check

All current BMW engines (M42 (from 1/94), M44, M52, S52, M60, M62 and M73 engines) incorporate a pressure-controlled crankcase ventilation system. If oil consumption issues are being diagnosed, this information can be helpful. The crankcase ventilation systems use various crankcase ventilation valves depending on the engine type as shown in Figure 1 below.
Although the valves all look different, they function similarly using a spring and diaphragm assembly to control the crankcase pressure. A properly functioning pressure control valve is designed to maintain a slight vacuum (approximately 10 - 15 mbar) in the crankcase which ensures reliable crankcase venting during all engine operating conditions.
A malfunctioning crankcase ventilation valve may cause the following complaints:
• Engine runs rough;
• Whistling noise from crankcase ventilation valve; and
• Check engine light on - possible DME faults stored: misfire all cylinders, oxygen sensor/mixture faults, etc.
To assist in troubleshooting the above complaints a special tool (p/n 99 00 0 001 410) has been developed to quickly check a pressure controlled crankcase ventilation system. Also refer to service information bulletin number 04 08 98 for further information regarding the slack tube manometer tool.
The slack tube manometer tool consists of:
1) Slack Tube Manometer
2) Connecting Hose
3) Modified Oil Filler Cap
Follow the instructions included with the slack tube manometer for the initial tool set up and general operating procedures. Basic operation is as follows:
1) Connect the slack tube manometer to the engine oil filler neck.
2) With both valves (1) open approximately 1/4 turn; zero the sliding scale using the knob (2) as shown in Figure 2, below.
3) Start the engine and observe the column of water.
4) With all electrical consumers and the air conditioning switched off and engine at operating temperature the reading should indicate from 3.0 - 6.0 inches of water at idle.

source: http://www.enginebuildermag.com/Content/Site302/SpecialIssue/02_01_2008/3555Import1pdf_00000005695.pdf