I've got a '76, I bled the brakes. It worked great for a couple if days then the pedal almost goes to the floor it will slow it down but won't stop it. If you pump it once you have hulk pedal again. Also if the park brake is on you have full pedal without having to pump it

 

I would say either the master cylinder or an internally broken hose at the wheel. To check the master cylinder, just take off the lines coming out and plug up the holes with bolts or whatever. The brakes should be hard as a rock. If not, or if they fade, the master cylinder is bad. Were you able to get fluid easily out of all four wheels?

 

Don t tear the master cyl apart !!!!!

If you have full pedal with the e brake on ,your rear drums are out of adjustment.
Check that first, when you pull , well stomp the ebake, you are taking up the free play, so your wheel cylinders dont have to move as far, so you don t have to push the pedal as far.
Do you have disks or drums in front?

If you have no idea how to adjust them, check youtube.

Where are the new pictures?

 

I agree it's probably the rear brakes because of the E brake statement. But, if you bled it once and it worked fine for a few days before it started doing it again then, I would suspect a bad wheel cylinder or that part of the m/c is bad. Could even be a rubber brake line to the rear. I don't think adjusting will help only because it got better when bled, also wouldn't suspect the m/c as much for the same reason. Somehow or other it's getting air back into the rear brake circuit.

 

I wonder if the wheel cylinders are over extended to the point they are leaking, and sucking air. Id start there with the adjusters.

 

Possible. hard to say with actually looking it over. But there should be signs of leaking I would think.

 

Was wondering why you had to bleed the brakes in the first place? Above info provided is valid, except for the plugging of the ports at the master cylinder with bolts, threads are not common. Be careful! But I do agree, sounds like an internal bypass of the master, its normal for them to be intermittent when failing. You know, work today, vacation, tomorrow.

 

Why would that not be valid? I've done that to many of my master cylinders to test them. All you have to do is go to the parts store and have them match up plugs. Any reason why you think its a bad idea?

 

Certainly valid with the proper plugs, i have used flare nuts and BBs, as long as you have the right threads , its fine. Some times its good to state the obvious, because the persons
reading could have less experience, or technical background, you weren t wrong at all, and one should allways be careful to make clear their clarifications. We Canadians like it peaceful like, eh,

 

plug up the holes with bolts or whatever. "Whatever" is not what I objected to, the "with bolts" bothered me. I can see screwing a NF threaded or a NC threaded bolt in tight enough to seal the port and messing up the threaded part of the master. People have a bad habit of flaming everyone on this site, that is nor was it my intention to do that. I could see a person being mislead and that is all. Sorry if I offeneded the person that made the statement.