Brake Bleed
 

Help....I own a 1981 vette(recently bought). My brake pedal is soft and goes all the way to the floor. I have tried every method of bleeding the brakes, I even bought the Motive Power Bleeder. I don't see any air in the lines, no leaks. But the pedal is the same. I really don't know what else to try. Could the Master Cylinder be bad? There is no fluid leaking around it? Short of taking it into a brake shop I really don't know what else to try. Any ideas?????

Sounds like a bad master cylinder to me.

I will try that...The pedal is hard until I start the car..then I can put it to the floor.
Thanks

Welcome to the forum. You could do a vacuum test on the power brake booster. You can also just pull the hose off and plug it and see if it still goes to the floor when you start it.

Thank you..I will try that

Help Please.... On my 81 vette I had brake pedal that went to the floor. Bleeding the brakes didn't help. I replaced all 4 calipers and a new master cylinder. Still had no brake pedal. SO..when I take the hose "off" the brake booster (the cars rpm goes up a little, BUT when I push on the brakes I have a hard pedal. " Does this mean the brake booster is bad??" There is good vacume coming from the engine hose. Do I need a brake booster or is it from something else..Thank you

Certainly looks like it.
It sounds like you might be running a little rich since the idle increases when you add more air to the system.