DO NOT PAY GIO PRICES
i had this same problem for a good year and a half, had no rear brakes.
when i would press the pedal and crack the bleeder valve open it would squirt the fluid out like there was pressure.. but the master was failing under pressure..
this is the person i ordered my brakes from on ebay.. 40 bucks for a whole new rear brake system.. this is exactly what i ordered and use..now i have rear brakes and no brake issues
http://cgi.ebay.com/ebaymotors/Rear-...Q5fAccessories