If you go to:
http://volkswagen.msk.ru/vw_01.htm
You can downlad a zip file for the 1991 Transporter (Vanagon).  There is
also the Caravelle (Eurovan), Corrado, Golf, etc.  In the zip file is
full of PDFs.  This is information from the Mitchell Repair Company,
LLC.  There's pages on bleeding of cooling system, tune ups, etc.

The site is russian, so I can't read a word, but the PDFs are in
English.
Don't know how worthwhile it is, but have a look if you like.  YMMV.

Keith Adams
Calgary, Alberta, Canada
1986 Vanagon GL Westfalia "Roxy"