master cylinder, or???........
 

I have had this problem for a few months now, and the past 2 weeks it has gotten worse. I knew I needed brakes in the rear and the front were pretty low too. I got the rears done (dont get involved with drums) and replaced the rotors and pads up front. My problem still exists, the pedal goes down like 80% when i press on the brakes. I noticed in the reservior that there is a lil sludge in the bottom. Could the prop. valve not be gettin fluid from a clog? Or it the MC just on its way out. Im new to workin on brakes and i dont wanna screw up something that may have to save me one day (I live in Jersey, so I need them working 110%) Any help will be appreciated.

The power assistor may be knockin on heaven's door. Check to see if you can create a vaccume? with car off. If the breaks were done right they would pull the fluid in or find a hole in the line to get something to fill the vaccume in the line.
my .02 though

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You put Mt. Dew in the gas tank!?!

Wow, look at it go!
1984 L69 305HO WS6 Firebird Trans Am
Current Mods[*] 2 1/2" Flowmaster cat back[*] gutted cat[*] 160 thermostat[*] all around polyurethane bushing kit from Energy Suspension[*] 3.73 Disk rear
Mods to come![*] 350 .30" SB [*] Comp Cam[*] Edelbrock RPM Proformer Package [*] 3.73 Posi Disk rear[*] Edelbrock TES headders - Yeah I like em![*] 150 lb shot Edelbrock Nitrous System[*] Edelbrock Aluminnum Signeture Series Valve covers.[*] 140 amp GM High Proformance Altnator