Need Help Getting a firm pedal

[Sparky Anderson]

I have a 1967 Plymouth GTX with a 440 engine and the 727 transmission. I am in the middle of converting to all disc brakes. Everything is installed however I can’t seem to get the pedal to firm up. It wants to go to the floor. I can get it to firm up somewhat by pumping the pedal but as soon as I let go and go to pump it again it goes to the floor.
My system consists of all new parts:
Double Diaphragm Bendix booster
Combination valve PV2
Master cylinder has a 1” bore
(Casting # 2225621)
There is also an adjustable valve installed on the rear brake line after combination valve
The rear brake calipers are of a Cadillac El Dorado (casting #s 184138 184139). These were put on by a reputable shop. They have also been adjusted.
The front calipers are the single piston (2.75”).
New rotors, bearing, hoses etc.


Is there something I’m missing.
I’ve bled the master cylinder and the brake lines more than once.

Have you tested your new master cylinder to rule it out, even though it's new, could be bad. Try blocking off both lines coming from it and your pedal should be hard as a rock. If not, it's a bad one, this has happened to me. If it's good u have air in the system if everything else looks good.

I have a 1967 Plymouth GTX with a 440 engine and the 727 transmission. I am in the middle of converting to all disc brakes. Everything is installed however I can’t seem to get the pedal to firm up. It wants to go to the floor. I can get it to firm up somewhat by pumping the pedal but as soon as I let go and go to pump it again it goes to the floor.
My system consists of all new parts:
Double Diaphragm Bendix booster
Combination valve PV2
Master cylinder has a 1” bore
(Casting # 2225621)
There is also an adjustable valve installed on the rear brake line after combination valve
The rear brake calipers are of a Cadillac El Dorado (casting #s 184138 184139). These were put on by a reputable shop. They have also been adjusted.
The front calipers are the single piston (2.75”).
New rotors, bearing, hoses etc.

 

[GageGtx]

Have you tested your new master cylinder to rule it out, even though it's new, could be bad. Try blocking off both lines coming from it and your pedal should be hard as a rock. If not, it's a bad one, this has happened to me. If it's good u have air in the system if everything else looks good.

That's one of the first things I did. Everything was ok. Guess there's still air somewhere