Well, back in the day, on our old cars, we could start the engine, let
it warm up, and open the radiator cap to see if flow occurred.  Can't do
that now (and haven't been able to in a long while).  If there is no
flow, that suggests a stuck thermostat (a new one can be bad).  The red
light is supposed to flash on startup, then go out.  If the engine is
not yet warmed up, then it is not overheated (duh).  But that doesn't
mean you don't have a problem.

Items you did not mention include the fan switch (it's on the radiator,
lower right as you look at the van from the front).  If the guage pegs
as soon as the engine is on, I'd suspect electrical, regardless of your
mechanic's opinion.  Check all the connections, as well as the fan
switch.  The guage itself could be bad, too.  Which sender did you
replace, the low coolant sender on the pressure tank, or the temperature
sender on the thermostat housing?

Good luck, David

On Tue, Dec 15, 2009 at 1:02 PM, Woody Halsey wrote:

> Well, after a couple of years of minimal use and maximal body work (my
> wife says that the V'gon is like an aging woman with a lot of face
> work:
> beautiful on the outside but ...) I decided to fix the
> overheating/pegging temp gauge problem once and for all.  New
> thermostat, temp sensors, water pump, radiator and fresh fill of
> coolant have NOT solved it. The mechanic who is doing the work for me
> now says he thinks a head gasket job is in order. Does this make
> sense?  *       There is no leaking around the gasket. *       The
> expansion tank is filled to the brim. *       The temp gauge pegs over
> and the red light starts flashing as
> soon as the engine is turned on. Can it be "overheating" if it is not
> even "warmed up?" *       Mechanic states there is no flow of coolant
> through the system.
> (Is it possible to check that with a stethoscope?) *       Mechanic
> insists that the problem is mechanical, not electrical.
>
>  Awaiting your wise suggestions before spending any more money,
>  Woody
> 83.5 V'gon
> Haverhill, MA    W. W. HALSEY II
> President
> T 978.725.6828 ext.115   M 978.204.5795   www.sya.org
>  439 South Union Street, Lawrence, MA 01843
> SCHOOL YEAR ABROAD