Just looking for a little help here with my '75 280Z. I was coming home yesterday and on the last turn before my house, I pressed the brake. My petal starts going down slowly but down further than it has before and makes an audible hiss when pressed. I checked the fluid and both fluid conisters on the master cylinder were half full. I topped off and (I know silly but had no choice) drove to work this morning. It stops. Kinda. But takes me 4 times the distance to stop and makes a hiss whenever pressed.

Master cylinder?

Master Vac?

Line?

 

My car is doing the same thing! I'm guessing it's the master cylinder. I just did a rear disk swap with a 15/16" master cylinder but the m/c I used was a used one. I can bleed till I'm blue in the face and I can't get a good pedal. I do notice that the front wheel brake lines do not flex as much as the rears do so I'm thinking that the front of the m/c is shot. Anyone else?
Joe

 

I just got about 10 posts back on www.zcar.com on this same question, seems like most thought it was the brake booster.