You have a coolant leak.  The easiest way to find it will be to have the
system pressure tested.  You could pressure test it yourself but the kit
costs about $150, may be worth the investment for a vanagon though.  The
pressure test is done by putting 15 psi or so on the pressurized coolant
tank with the engine off.  If the system holds pressure there are no
leaks.  If theres a leak it will not hold pressure and be easier to find
with the engine off.  The vehicle may have to be warmed up so that the
t-stat is open when the pressure test is done.  Tools and techniques like
this are why it takes your mechanic 30 minutes to find the leak and you
all day.

Andrew Fox

On Thu, 24 Jul 2003, Joe Glisson wrote:

> I'm losing coolant and can't figure out where it is going - no leaks that I
> can detect. I would appreciate any ideas or suggestions as to how to figure
> this out - when the coolant gets low enough I get air lock and it runs hot.
> Any help would be appreciated. Thanks, Joe
>