Heres a handy little site I found a few years back.
Anyone interested what the guts of a metro/mgf hydrogas unit look like:
http://www.mgfcar.de/cut_unit/index.htm
Heres some pics of what one kind of broken hydrogas can look like (symtom wise):
http://www.mgfcar.de/hydragas/blownhydra.html
and here:
http://www.mgfcar.de/hydragas/blownhydra2.html

