Ben, you need to get rid of the mechanic working on your bus, not the bus, fast
- very fast!  This wahoo is missing some very basic Vanagon principles if you,
as the owner, have to ask if coolant system needs to be bled.  If I were you I'd
(1) have your "mechanic" replace the tstat he welded open with a brand new one,
at no charge for parts and labour; (B) have your mechanic (again, I use the term
loosely, if not tongue in cheek) flush, fill, and bleed the cooling system per
the instructions found in the archives of this list, with a phosphate-free
coolant YOU provide - the theory being that if this guy would weld a tstat open
and does not know how to bleed a Vanagon cooling system, he sure a hell isn't
going to know about the phosphate-free coolant; (III) find a mechanic in your
area that knows Vanagons; (d) Get yourself a Bentley repair manual - if nothing
else, it makes great bathroom reading.

My $.02...

Alan Bosch
Phred ('88 Wolfsburg)