It won't damage anything, but it could be condsidered a bit of a fire
hazard just sitting still.  The gasoline vapors will be released to
atmosphere at the leak points.  You'll smell fumes on a hot day, and at fill
up time.
  I drove my van with a broken plastic crossover vent tee for almost a year
before I did a reseal.  The crossover is connected to the same vent lines as
the expansion reservoir check valves.
  They are not 'float' valves; they are weighted check valves that will stop
the flow of fuel in the case that you (accidentally) fly inverted.  Any
leaks along this system will result in an unsafe (and polluting!) condition
due to fuel vapors being released to atmosphere, instead of being trapped
and re-introduced to the intake upon startup.
  Don't totally top-off the gas tank (to prevent overflows), and expect some
gas smell when you approach the door on that side of the van, until you get
it resealed.

HTH,

Mike B.

----- Original Message -----
From: "Taeke" <taeke.t@GMAIL.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Thursday, July 03, 2008 2:56 PM
Subject: Re: Driving without fuel expansion tanks hooked up?

I need a reseal what's a float valve?

-----Original Message-----
From: Damon Lowe <dlowe93@COMCAST.NET>
Sent: Wednesday, July 02, 2008 11:00 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Driving without fuel expansion tanks hooked up?

My wife suddenly decided we need to take the westy to see fireworks this
weekend, which would normally be super cool.  However I currently have my
fuel expansion tanks out while waiting on some "float" valves that broke
while doing a tank reseal.  Will I damage anything if I put a small amount
of gas in and drive it with the lines to the charcoal canister unhooked?