Duh!  It doesn't have to be a compressible fluid!  Given a fixed volume and
an increase in temperature (yeah, the engine's running . . . ), you'd HAVE to
have an increase in pressure . . .  It's all coming back to me now . . . I'm
having flashbacks to the days when I failed thermodynamics in college!  Some
days it just doesn't pay to get out of bed . . .

Thanks Tim, for giving me back my perspective,
Marc

t wrote:

> Marc Perdue wrote:
> >
> > This doesn't make sense to me.  The cooling system in the Vanagons is a
> > pressurized system.  Unless the coolant is a compressible fluid such as
> > freon, it seems to me that you'd HAVE to have SOME air in the system.
> >
> > What am I missing?
> >
> > Marc Perdue
> >
>
> The expansion tank with a pressurized check valve.