Update:

The problem with my car turned out to be a defective heater control valve. This is located on the driver's side frame rail. There are a couple of solenoids that control flow independently to the left and right side of the car, and the one that controls the driver's side was stuck in the open position. Once this was replaced, all was good.

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2014 BMW 328i Xdrive
2011 BMW 335i M-Sport
2008 BMW X5 4.8i Sport
2000 BMW 528i 5sp