There is a little nut on the bottom of the tube that is secured by a plastic "washer". I had to destroy that washer to unscrew the nut but I was able to tighten things back up later without the washer.
Carefully slide the "innards" out of the tube and all will be revealed,
Be very careful not to damage the 2 fine wires that the float slides on.

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1981 240D 143k 4 spd manual -SOLD

2004 VW Jetta TDI 5 speed 300k -still driven daily