Gary is right, cooling just the radiator does have an almost
instantaneous effect on the cooling system pressure. I had a pressure
gauge and pump on a Vanagon cooling system a few weeks ago trying to
find a leak. With the engine hot and running at a fast idle the pressure
in the system would drop by several PSI in a few seconds each time the
fan started and then slowly climb back up after the fan shut down.

I put the lowest temp switch I could find in one of my Syncros this
summer but took it out when the fan started running way too much on warm
days.

Mark

Gary hradek wrote:

> Mathew, mathew, mathew,
>        yee of so little faith, if I did not know
> better I would say yeh name is thomas.
>     The after shutdown cooling fan action is about
> cooling the radiator and coolant in the radiator not
> the motor.   By this air flow, overboiling is
> prevented.   It's the old pv equals nrt equation.   If
> T temperature  goes up than pressure and or volume
> goes up and coolant goes pissing our the back blue cap
> into the overflow everytime you shut off a hot engine.
>
>      Which brings me  to my busdepot question.
> Busdepot sells a sensor switch which is a lower
> temperature switch for the two speed radiator fan.
> Does anyone know if it works better?
>           thanks gary
> Date:    Mon, 29 Sep 2003 09:30:49 -0700
> From:    Matthew <poll7356@UIDAHO.EDU>
> Subject: Re: fan switch or sensor
>
> yes, but it is stupid. On the a2's the fan will pull
> air through the
> radiator and over the engine to cool it. Whereas the
> vanagon will pull
> air over the radiator but that air doesn't get over
> the engine nor does
> the coolant cycle. What is needed is a small electric
> pump that will
> cycle coolant while the after-run coolant fan is on.
> Unless there is
> enough thermo-syphoning going on to make it work.
> Doubt it.
>
>
>
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