On Tue, 9 Mar 2004, Jonathan Farrugia wrote:

> i was able to find valving to vent the tank as pressure
> built up but, i was unable to find valving that would allow the system to
> draw coolant back into the radiator from the over flow bottle as the
> system cooled and the system experienced a vacuum.  if any one knows of
> such off the shelf valving i would be interested to know about it.

How about an ordinary check valve?  Orient it so it only passes coolant
from the tank to the radiator, and insert it as a bypass around your
pressure valve.

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