No brakes

[85 ttypewh1]

Earlier today i was driving and the brake pedal was kind of low, i would let up on the pedal and press again lightly and it would be ok.I stopped and checked the fluid and it was about half way down the res. so i topped it off with dot 3 and drove back home, all was fine. Just came back from taco bell and on the way there it did it again and every time i pressed the pedal it got lower, so i got my food and drove home slowly and pulled it the drive way and applied the brakes and the pedal was low and i contiued to push and it would go to the floor and when i let off it would spring back up and then i can push it to the floor again, it does have some resistance like a big spring but i can still push it to the floor i did notice when i first apply the brakes i hear a click under the dash. Its dark out and cold so i did not look for leaks but i did earlier when i topped the fluid off the first time and did not see any under the hood and when i came home tonight i push the pedal to the floor a few times then put the car in the garage and looked for a puddle in the drive and saw nothing. Funny thing is i was thinking about doing a vac upgrade in the future but i may have to do it sooner. I will check the car out tomarrow, any ideas, sorry to be so long but i was a mech. some years ago and i know how it feels not to get the whole story. Thanks for any help.

 

[85 ttypewh1]

I replaced the master cylinder today and bench bled it and bled the brakes, took the car out and it stops great but if i push on the pedal harder it goes to the floor, the car does stop normal. i have just never noticed this before is there some kind of relief that keeps the lines from building too much pressure it is the hydroboost. When i turn the key off and mash on the pedal it is firm and still has about 2-3 inches till it hits the floor with me pushing pretty hard, is this normal for the system or is something else wrong

 

[85 t-tizzle]

the same thing happend to me today im gonna change out the master cyl tommow i hope that fixes it .

 

[85 t-tizzle]

good post changed out master cyl brakes work great now