Disk brake peddle pressure

[Sandemonium]

I have a 69 chevy pick up with CPP 4 wheel disk brake package with brake booster and proportioning valve and when i press the brake peddle it seems like i have to push it once to build up pressure then press it a second time to get good stopping power what can i do to resolve this? Thank you.

[Bus Ted Knuckle]

Sounds like you need to bleed them again. Start with the wheel farthest from the MC and work to the closest.

[Sandemonium]

Thanks for the suggestion. I have bled them several times and nothing in the operation changes. It seems like when you brake the first push of the peddle the brakes act like non-power brakes, the second push of the peddle the brakes work much better, but nothing like a newer type car disk brake.

I may try to bleed them again this weekend.

Thanks again for your help.

Bob

[Longhorn Man]

if it is a complete kit, then call them up. They back up there stuff. Something isn't right.

[LONGHAIR]

It is possible that you have a warped rotor...this can push the pads back in the caliper as you drive, this will lead to the double pump situation.
A bent rear axle could do the same thing, it would make the rotor "wobble" in relation to the caliper. As long as the wobble is slight, the caliper can move with it and you may not feel it in the pedal, but when there is no pressure applied, it would knock the pads back.

[cdowns]

are the calipers installed with all of them having the bleeder screws on top?

[msgross]

did you install new soft lines as well? from the frame to caliper?

[cparman]

are the rear calipers the ones with the lever that bolts to the back side of the caliper to set the emergency brake? IF SO:
longhair could be right
cdowns could be right
I have a very low opinion of this type of brake caliper because of the low/no brake pedal issues. Here are my suggestions.
MAKE SURE YOU THINK THERE IS NO AIR IN THE SYSTEM
MAKE SURE THE BLEEDERS ARE UP
attempt to ratchet the levers on the back of each caliper. This will adjust the mechanical part of the brake caliper piston to remove any clearence between the brake pad and the rotor. When you get to this point, a drink of water, and a walk away. remove the brake master cylinder WITHOUT removing the brake lines. find a bit of playdough or something that will compress and put it on the end of the shaft that comes out of the brake booster. Bolt master cylinder back to the booster. ANOTHER drink of water, and remove M/C again. see if the playdough got squished. If it did not ( gets tricky here ) see if the rod in the booster looks like it would be able to unscrewed to make it longer. IF NOT, see if you can remove it and make it longer. My experience is two fold. I have done probably 20 + disc brake conversions on different brands of cars, and the final tweek to make an old car have new car feeling brakes is to figure out this adjustment. The playdough is the acid test. if it squishes it is not this adjustment and look elsewhere. If it does not squish put your efforts here. be careful when working here as if you make the rod a bit too long the pedal will feel great, but build pressure after a 5 -10 mile road test. I just finished a 56 Mustang ( longhorn man ) and it took a bit of fiddling to make me happy with pedal height. sorry for being long winded

[Sandemonium]

Thank you all for the replies.

I do have new soft lines both front and rear. Calipers have the bleeder screws facing up. I also have new axles and rotors so although I dont like to assume, I would like to think everything is straight.

The rear calipers are the type that have the emrgency brake lever, but at this point I have not attached the emergency brake linkage.

I will attempt to bleed the system again, and I will rachet up the emergency brake adjusters ( actually this could be a large part of the problem) to set the mechanical action of the caliper.

As it is now when I push the peddle the first time the brake light on the combination valve is activated and when I push the peddle the second time the light goes off and braking action seems much better, but I think it should be much better than it is.

If the above items don't seem to improve the operation I will attempt to play with MC and rod length.

Thank you all for the help and suggestions I will give it a try and let you know what I find out.

Bob

[Scottshotrods]

do you happen to know what size
is your bore size in the master.You
should be runnning a 1 1/8 bore size.
When you are running 4 wheel disc.When you run disc and drum
you will use a 1 inch bore size.

One more thing to add your booster
could be bad as well.If you have any questions please call us (805)
485-0382
Thankyou,
Justin
www.scottshotrods.com

[msgross]

did you "bench bleed" your MC before installing it?

[Andy4639]

The vacuum is good on the booster. If you have a modified engine you may need a vacuum canister in the line to hold the vacuum while driving.