It is possible that the clutch MC internal seals have gone bad.  That is why
you can push it and nothing happens.  Then it started leaking externally when
you kept pumping it.
I have these clutch master cylinders, new, FAG, German, with the VW symbol on
the side for $35 (list member price).  Forget about rebuilding it, just slap
a new one on there and forget it for the next 18 years.
Hope this helps.

Thanks,
Ken Wilford
http://www.vanagain.com
John 3:16
Phone: (856)-765-1583
Shop:   (856)-327-0027
Fax:     (856)-327-2242