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Since the engine was hot (at operating temperature) we chose not to perform a smoke leak test but connected our monometer (Slack Tube Tester), the crankcase vacuum was very high, (off the scale). We disconnected both vacuum vent valves on top of the valve covers and blocked the vacuum pipes to the throttle body eventually determining bank #1 to be the cause. We removed the suspect faulty bank #1 vacuum vent valve, it was torn (arrow).
You can buy just the vacuum vent valves (repair kit) PN 11.12.7.547.058 separately (low cost) from BMW. Now the crankcase vacuum reading is normal at around 7.75" of water.
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