It's held in place with a small hose clamp that attached it to a small tab on one of the metal coolant pipes.  There is also a small green "o" rign that seals it to the case.  yours is likelly hard and brittle and stuck in the recess in the case.  I've never replaced one with the motor in the van so I dont' know how hard that would be to do.
 
Pascal
84 Westy

________________________________

From: Vanagon Mailing List on behalf of Shawn Luft
Sent: Sun 10/06/2007 8:31 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Oil dipstick loose

The nozzle piece that holds the dipstick is loose and detached from the
engine on an '86.  How can I get the nozzle re-attached snugly to the
engine?  Is this press fit into place?  Should it be cleaned with degreaser
and bonded back into place?

Thanks!
Shawn