Roy,

Part one:

Without more info, hard to tell if coolant sensor is really your
problem.  It was the culprit for me, but mine ran great until it had
been running for around 45 minutes.  About then, when it was good and
warmed up thru and thru, is when it started loosing power and ran
horribly, sputtering along the side of the road.  Only 'fix' was to let
it cool down. My sensor was giving too high of a reading - i.e. the
brain thought the engine was hotter than it really was so in
self-preservation mode was cutting the fuel supply.

It sounds honestly like something else, something letting too much air
into system.  It starts working good when the O2 sensor kicks in and
compensates (while it comes in handy, its probably going to die an early
death because of the 'real' problem).  As an experiment, try
disconnecting the O2 sensor.  If the O2 sensor is compensating for the
"real" problem, then the problem should not go away when warmed up.

Like I said, hard to tell that your symptoms point to this.  HOWEVER,
for the 87 (mines an 87), the sensor and o-ring cost a total of $12 at
the dealer.  In my mind, my time is worth more than that so it was
cheaper to replace than to test.  To each his own.

Part two:

Does if fail with time?  Of course it does.  Everything does.  Mine had
around 115,000 when it started causing problems.  When I took it out it
did not look pretty.  This sensor has absolutely NOTHING to do with the
needle.  A different temp sensor goes to the needle.

Good luck,
Tonya
87 Vanagon GL Wolfs

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