A few months ago I had my '90 Vanagon's fuel tank replaced ($650) because
it had sucked itself into a crumpled and leaky shape.  Some part of the
system was malfunctioning in a way that put a powerful vacuum on the tank.

It just started doing it again this week - I can hear the tank going
"poing" as it deforms inward, and there's a "whoosh" when I open the gas
cap.

Any clues as to where the failure might be?
Is the cap supposed to be vented? (and it's plugged now?)
Where else is there pressure-equalization in the system?

I'd prefer not to have to replace the tank again...

bcnu - Grungy (John Gladu)     (Houston, TX)    grungy@mindless.com

'60 dddPanel walk-thru / '90 Vanagon / '68 & '69 Bugs / '93 Eurovan