pressure brake bleeding help - am I clueless or just forgetting something?

[Huw Powell <human@nh.ultranet.com>]

OK, I've borrowed my neighbors pressure bleeder.  It's about a 2 gallon
tank with air in the bottom, under a diaphram and fluid goes in the
top.  Done that, in fact there is obviously pressure at the mc, since
the reservoir is bulging a bit (uh-oh!).  But when I loosen bleeder
screws, expecting a torrent of fluid, all I get is a little drip - what
am I forgetting?  Anyone know or have a good guess?

Thanks hugely in advance!

-- 
Huw Powell

http://www.thebook.com/human-speakers/audi-main.htm