Some T shaped expansion valves had a bypass tube as a safety. I believe this is what this certain schrader is for,

I had an old Honda with this, The factory TXV had a bypass, the replacement one bought for it didnt have it and the little package of the TXV had a brass cap for the left over port in the evaporator.

The sensing tail of the TXV has no business with directly touching the gas. It is clipped onto the metal of the evap tubing.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)