Pat, the thermostat doesn't snap open and shut, it's gradual.  It will keep
the water flowing past it at <roughly> the same temperature -- until it's
wide open.  At that point, any additional heat input will drive the
temperature up.  The fan does the same thing at the other end of the
system, i.e. when the thermostat in the radiator switches on, the fan
operates and drives the temp back down until the radiator cools and opens
the switch.  So at those two points you can say roughly what the
temperature is.  However there will be places in the engine where the
coolant is hotter, and this will vary both by cooling system condition and
by the design of the motor.  The working limit is whatever is the boiling
point of coolant under about 13 psi pressure; when you pass that you get
steam and high pressure in the system >> venting coolant into the overflow
bottle etc.

So anyway, if your gauge stays put, that means that the thermostat isn't
fully open, and you have excess cooling capacity without engaging the fan.
When it rises and the fan comes on, your excess (if any) is the amount of
time that the fan does *not* run.  If the fan is running continuously and
the gauge still rising, you're about to overheat.

hope this helps...
david

At 00:06 3/28/99 -0500, Pat Dooley wrote:
>the current thermostat discussion makes me wonder exactly how hot the
>coolant gets in a fully warmed vanagon engine.  the thermostat may open at
>80 or 87 degrees c, but how hot does the coolant actually get?  the cooling
>fan should regulate the operating temp to a specific range.  i didn't see
>any specs in the bentley.