Glad it's getting fixed. Would a short bolt work well as a temporary plug?

Since the car is new to you, and I'm guessing you have not taken off the famous stiffening plate with its infamous bolts yet, you might want to look there for the missing check valve. Amazing sometimes what that plate can catch. First time I had that off on my car, I found the plastic cover for the positive battery jump port.

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2001 X5 3.0i, 203k miles, AT, owned since 2014