[200q20v] Leaking hydraulics; not a hose or the rack.

[steve_scalmanini at agilent.com]

Does anyone know how to troubleshoot a hydraulic leak that's 
not due to a hose or it's connections?  Mine started dripping 
~ a month ago. I replaced the return line to the reservoir (it'd 
been leaking veeery slowly for years, but never enough to drip) a 
week ago so now both it and the high pressure line are looking 
clean and sound, but the leak that started ~ a month ago continues.  
' seems to be coming from up high around the pump (maybe underneath
it) but I haven't been able to see the source.  The three hose 
connections on top look fine.  

Does anyone know where the likely source is?  
What's the replacement effort like?  ' looks not simple to me. 

Steve