ok just finished some wiring issues on my 72 cutlass s and now on to the brakes. here is what ive done and what is happening, front disk conversion with new master and booster new brake lines all the through and new wheel cylinders in the rear drums, now the issue is it will not build pressure, i bench bleed the master bleed the whole system the 2 person style, gravity and with a mityvac bleeder, but still no significant help to the spongy pedal. also when the car is running pushing the pedal down cause the idle to increase, i am really not sure what is going on with this and what i am missing. thanks for any help.

 

Sounds like you have a vacuum leak if the engine rpm increases like that. Check your connection at the booster and the intake. When you bled the brakes, did you start with the right rear, left rear, front right, front left? You might still have some air in the lines. How are the connections at the proportioning valve - no leaks? All the brake lines are snug and not leaking. Ok I know this may sound like it's talking down, but it's not. Just trying to find more info about what you've checked or not.

The brake pedal should feel a 'little' spongy on 72 power disc brakes but should apply braking pressure. How do you know the system is not building pressure?

 

Bad booster - and maybe master. too!
Where'd you get the parts?
Also, the proportioning valve is different from drum/drum to disc/drum.

 

i bleed the brakes from the farthest wheel and worked toward the closest wheel. the disc setup came as a completely new set master, booster, valve, spindles etc. there are no leaks and the brakes do grab it just seems like there should be some resistance on the brake pedal. also how can i find a vacuum leak i have replaced every vacuum line including booster to intake. the old brakes which were drums did the same thing even the idle increase so could i have two bad masters and boosters in a row or is something else i have done wrong.

 

feeling a little stupid, had the wife pump the brakes while i was under the car and turns out the soft braided line that connects at the caliper was leaking on both sides and was running down a path i couldnt see and collecting in my wheel dollies, tightened and bleed the brakes again and they are solid, thanks for the input allen and rick

 

Glad you got it fixed. Now - REALLY IMPORTANT - Flush those wheel dollies with water right away. If you leave the brake fluid sitting in there it can start dissolving your tires. As you probably know BF is highly corrosive.

 

Water's not really enough - I'd use brake-clean!

 

I prefer denatured alcohol ("wood alcohol") myself. I wash all my tools with it after brake work.

- Eric

 

i did flush the dollies even though the tires are being replaced, thanks again