Failed crank case vent

  • Maybe this will help someone else sometime ...

    Note: This applies to the 8 cylinder engines, don't know if this is the same on the 12's.

    Symptom: Very rough idle, poor running, and large clouds of whitish/blue smoke.

    Cause: failed crankcase vent valve

    Fix: Replace valve

    The easy way: Remove the cover on top of the engine, the sound insulation from the top and the back of the engine, and the housing that holds the micro air filters from the firewall. Remove and replace the valve that is on the back of the engine. Be careful not to pull the vent tube rearward and off the fitting at the front of the engine when removing the valve.

    The hard way: Do the above, and remove the intake manifold. This allows you to clean all the oil out of the intake manifold, and replace the 'o' ring inside the front of the vent tube.

    The BMW Engine Adventure

    The engine with the intake removed

    This is the reason for removing the intake, the tube has an 'o' ring inside that cannot be changed with the intake manifold on the engine. You might be able to able to remove the throttle body, but that too is pretty difficult with the intake on the engine as well. Easier to just remove the intake manifold, besides, this way I was able to clean all the oil out if it.

    The Throttle body removed and cleaned

    The intake manifold removed from the engine

    Note the brass inserts in the plastic housing

    The failed crank case vent valve, there is a diaphragm inside this that fails. When this happens, the engine will run very roughly due to a lean condition caused by outside air drawn in through the engine seals as a result of excessive vacuum. This will be accompanied by scary amounts of whitish/blue smoke.

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