On Mon, 8 Mar 2004, George Goff wrote:

> 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.

I've heard claims that the "free oxygen" introduced to a cooling system by
having air entering and exiting the expansion tank increases corrosion,
but I've never really believed this.

Heck, Ford was making vans with no overflow bottle or expansion tank at
all as late as 1990.  The manual told you to leave an inch of air space in
the top of the radiator when filling it, to allow for expansion.  After a
while I got tired of it puking coolant out on the ground when I misjudged
this, and added an overflow bottle myself.  I don't like seeing a coolant
puddle under my car.

David Brodbeck, N8SRE
'82 Volkswagen Diesel Westfalia
'86 Volvo 240DL wagon