Dennis is exactly on target.

Check the little hose from the expansion tank cap to the over flow tank,
be sure it doesn't have a leak. Then fill the expansion tank, put the
cap back on. Run the engine until warm. As it warms, the coolant will
expand increasing the pressure on the cap and the coolant will flow into
the overflow tank. Shut the engine down, allow it to cool. If there are
no problems with the cap or hose, the coolant should be siphoned back
into the expansion tank as the coolant cools down. The overflow tank is
vented with three holes in the back side of the tank towards the rear of
the vehicle up at the top.

However --- if the coolant exits the expansion tank, and the coolant
level in the expansion tank drops with nothing to replace it, then in
all likelyhood - as Dennis has said - you have a head leak and
combustion gases are escaping into the coolant, collecting in the
expansion tank, and pushing the coolant out. The over flow tank then
becomes a vent for the expanding combustion gasses and displaces so much
coolant that it cannot be recovered. As the engine cools after shut
down, the exposed end of the hose in the overflow tank simply sucks air
and  because the ends of the probes on the sensor are exposed, and the
system reads an open circuit like that as "infinity" resistance .... and
the red LED on the temp guage comes on.

Go Luck.

John Rodgers
88 GL Driver

Dennis Haynes wrote:

>Nope!
>Either the system is not fully filled, (air in system), or the pressure
>cap is not holding, or most likely you have an internal head leak
>filling the cooling system with combustion gases.
>
>Dennis
>
>-----Original Message-----
>From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf
>Of dusty edwards
>Sent: Sunday, February 05, 2006 1:21 PM
>To: vanagon@GERRY.VANAGON.COM
>Subject: Blinking Coolant Light Mystery (to me)
>
>so, the coolant light seems to begin blinking once the van is warm.
>i've learned a little about this scenario while searching the archives.
>
>the fill tank is full, but the expansion tank is at (or below)
>minimum..........should it be that way?
>
>any suggestions?
>
>thanks for your help!
>dusty.
>  |___|_|_|__\
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>  "(o)-----(o)--"
>
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>