At 01:04 AM 7/22/2010 Thursday, David White wrote:
>My 87 vanagon won't start once the engine is warm. But if I unplug the
>coolant sensor and crank it a few times (it still won't start), then
>plug the sensor back in, the engine starts right up. Why and what's
>the fix?

If you're talking about the coolant level sender, then it's a
complete mystery.  If you're talking about the Temp-II sender in the
thermostat housing, get it into the no-start condition, then with
ignition on use a needle to pierce the insulation and measure voltage
to ground of both leads.  The ground should be essentially zero, and
the other should be only a tenth-volt or two.

If they both read 5v you have a bad ground.  If one reads 5 and the
other zero, you have a bad connection somewhere between the two
points you're measuring on the wires.  This could be from wire to
female terminal, female to male terminal, or internal in the
sender.  My guess would be wire to female terminal closely followed
by a female terminal that needs to be tightened by squeezing, with an
internal sender open the least likely under the circumstances.

Take some measurements and report; we'll go from there.

Yours,
David