Need Help Getting a firm pedal

[GageGtx]

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.

 

[steve340]

Sounds like air somewhere. You can gently clamp rubber hoses to help find were it might be trapped.
Do you see any fluid leaks?

 

[GageGtx]

Sounds like air somewhere. You can gently clamp rubber hoses to help find were it might be trapped.
Do you see any fluid leaks?

I see no visible leaks. Can you elaborate on your clamping hoses ?

 

[Don Frelier]

Are all the bleeder screws at the highest point on the calipers?
If not you will never get all the air out.

 

[GageGtx]

Are all the bleeder screws at the highest point on the calipers?
If not you will never get all the air out.

The rear ones are however the front ones are not. How would I fix that when that’s the way they were made?

 

[steve340]

You clamp the flexible rubber hose to say isolate the rear brakes etc.
You can buy tools cheaply.
Post #4 from Don is your problem.

 

[Don Frelier]

The rear ones are however the front ones are not. How would I fix that when that’s the way they were made?

Two ways:

1. Sometimes you can swap the spindles and mount the calipers towards back if they were in front or vice-versa.

2. Unbolt the caliper from mount and find/make a block of wood to insert where the rotor would be then rotate in free air until the bleeder is at the top. You might need a helper or rig up a wire or something.
Bleed the air out and then re-install on the mount.

 

[GageGtx]

Two ways:

1. Sometimes you can swap the spindles and mount the calipers towards back if they were in front or vice-versa.

2. Unbolt the caliper from mount and find/make a block of wood to insert where the rotor would be then rotate in free air until the bleeder is at the top. You might need a helper or rig up a wire or something.
Bleed the air out and then re-install on the mount.

I will give that a try this afternoon. Thank you

 

[steve340]

You are probably better off to sort the problem at this point - swap spindle position, side etc.
It will make maintenance in the future much easier.

 

[GageGtx]

You are probably better off to sort the problem at this point - swap spindle position, side etc.
It will make maintenance in the future much easier.

I will do that this afternoon hopefully and post back the results. Thanks

 

[eldubb440]

arent the bleeder holes and hose inlet holes the same, and can be swapped top to bottom??

 

[Don Frelier]

arent the bleeder holes and hose inlet holes the same, and can be swapped top to bottom??

Not necessarily (might have the copper washer setup with a banjo bolt).
Hose length might prohibit connecting to the other end as well.

 

[R/T Boy 67]

Swapping the calipers side to side will change the bleeder position. While you are in there, you should make sure the calipers are mounted to the rear if you have the stock swaybar. If they are mounted to the front, then you need to swap the knuckles.

 

[R413]

You can leave calipers on the side they are on, remove them and rotate so bleeder screws are at the top. Put a block of wood snug between pads and now bleed out the air. Reinstall calipers.

 

[Black_Sheep]

If you have a Wilwood adjustable proportion valve, turn the adjuster all of the way in before bleeding the rear brakes.

How Does a Proportioning Valve Work? And How Do You Adjust It?

The bleeders on the front disc calipers must be at the highest point in order to purge all of the air from the system. Also take care to pump slowly when pumping the pedal. Vigorous pumping can disperse trapped air into thousands of smaller bubbles.

 

[GageGtx]

Thanks for all the replies.
I took the front Calipers off and arranged them so the bleeder screw is on top. That did help some after bleeding them a few times however I think the pedal could be a bit firmer yet.
Do you think the 1" bore master cylinder is enough? Too much?

 

[RemCharger]

I found that the bendix boosters do have a bit of " squish" to them

 

[GageGtx]

Ok bc it's not bad now the way it is. I could possibly live with it.

 

[steve340]

On a power brake car the pedal is a bit closer to the floor boards than a manual brake car.
Did you set the adjustment on the booster pushrod? I guess the Bendix has one - can't remember.

 

[ckessel]

Blue pill? Oh wait, you're talking about the brake pedal.