In a message dated 3/8/04 6:25:47 AM, dhaynes@OPTONLINE.NET writes:

<< The main expansion tank is not large enough to allow for this without
becoming air bound when cold and overflowing when hot so the second tank is
needed.>>

If this were the reason, VW would have simply designed a larger pressure tank
instead of going to the extra expense and complexity of using two water
bottles.

<<Another advantage is that without air in the pressurized system, the
coolant is less likely to carry entrained air/O2 which avoids cavitation, internal
pitting and corrosion. >>

As is demonstrated by the billions of cars running around with air bubbles at
the top of their pressure tanks, this is no reason for the design either.
Cavitation as a result of air ingestion is never a problem on a properly
functioning coolant system.

The Vanagon's cooling system is what it is because of the geometry of the
vehicle with which the engineers had to work.

George