I asked about O2 sensor function and the braided protective sleeve that
surrounds the emerging wires from the top of most O2 sensors.  I was
thinking mine was not functioning, due to me seeing an overly-cool
operating temperature on my coolant gauge and my fuel gauge indication my
tank was emptying quicker than it should..

  The General Wisdom is when a problem occurs one should go the the last
area of work done and re-check to make sure you haven't messed something
up.   I recently  replaced my clutch slave and my o2 sensor is right
adjacent to where I was working...so I wrongly assumed I'd perhaps messed
up the O2 sensor connections or that a rather messy oil leak from my axle
seal was causing me problems in that area.
   I spent (wasted) a few hours checking all those connections and messing
around under there and couldn't find a thing wrong..

  So I thought, 'well, maybe cleaning up everything and checking it all,
that fixed something I didn't see'   Then I went windsurfing with my van,
and "Voila!...The temperature gauge was behaving as normal again and the
gas gauge showed I'd miraculously gained about 1/3 tank of gas.....As I
drove along through the Columbia Gorge to my favorite windsurf spot...it
dawned on me that I'd probably gotten some brake fluid from my messy
bleeding job, while working on the slave cylinder, got some brake fluid
onto my instrument foil or something...and it had dried up overnight.

  I did go back to the area of last work to recheck but I just didn't go
back to ALL the places where I was...    I have been fooled before by the
Vanagon instruments,  This time two gauges, seemingly unrelated in the
functions they indicate, were giving me numbers that were *close* to what I
expected, but not quite *right*.

  So anyhow, if you spill brake fluid during a brake bleed, you too could
spend some quality time under the van looking for something when the
problem may be up on the dash...

   Me dumb!