Here's a link to two pages of discussion on the subject on the Samba:

http://www.thesamba.com/vw/forum/viewtopic.php?t=480157&highlight=expansion+tanks

From: Jeff Lincoln 
Sent: Tuesday, November 08, 2011 1:53 PM
To: Ed Duntz 
Cc: vanagon@gerry.vanagon.com 
Subject: Re: '85 1.9 - Water in the Gas Tank

Ed,

Thanks for the inout. I guess this could be it - I didn't do much with those tanks when I resealed the gas tank. I just ran new hoses to them. I'll check them out for sure. 

This leads me to another question for everyone. I'm not much for altering things fromt he way they were designed but what is the risk (if any) in just eliminating those expansion tanks from the system entirely?

-- 
Thanks,

Jeff
'85 GL (Gertie)
'90 Carat (Grover - the noble parts donor) 
'78 Bus (Melissa) Patty's Bus