Testing and Inspection , Crankcase Ventilation System Check

All with M42(from 1/94), M44, M52, S52, M60, M62 and M73 engines.

Situation: All current BMW engines incorporate a pressure controlled crankcase ventilation system. The crankcase ventilation systems use various different crankcase ventilation valves depending on the engine type as shown in the illustration below.
(1) M52 / S52
(2) and (3) M73 uses two valves per engine
(4) M42 from 1/94 production / M44
(5) M60 / M62

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 assures 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
-Check engine light on - possible DME faults stored: misfire all cylinders, oxygen sensor/mixture faults, etc.

Note: DME faults stored in memory will vary depending on the DME version.
To assist in troubleshooting the above complaints a special tool part number 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 proceedures.

Connect the slack tube manometer to the engine oil filler neck.
With both valves (1) open approximately 1/4 turn, zero the sliding scale using the knob (2) as shown in the illustration below.

Start the engine and observe the column of water.

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.

Note: The values on both sides of the slack tube must be added together to get the proper reading as seen in the illustration below.
Example: 2.5 + 2.5 = 5.0 inches of water (The readings may fluctuate 0.1 to 0.2 during the measurement which is normal and does not indicate a defect.)

If a crankcase ventilation valve is defective (damaged diaphragm) the column of water will indicate an off of the scale reading (all of the water on one side of the slack tube) which indicates a high crankcase vacuum.

Note: A higher than normal crankcase vacuum will also cause the crankshaft seals to leak outside air into the crankcase during engine operation. A whistling or howling noise is usually heard coming from the seal areas (front or rear) at idle when this occurs.

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