Brakes sticking... I need your help

[AJohn6]

I installed the CPP power brake and rear disc conversion kit on my '71. i am having a problem with my master cylinder, I think. While driving the truck I can reach down and pull the brake pedal back about 1/4-3/8 of an inch. It doesn't do it all the time and I have tried adjusting the little post that comes out of the booster. I got more play out of the pedal but it still does it. I have new brake calipers and associated parts installed as well. I can tell its causing the brakes to have slight pressure on them because when I forgot to pull the pedal out I stopped and felt all of my rims and they were hot as heck. When I don't forget they feel fine. I am at a loss, and I need some trusty advice from you guys.

Thanks in advance,
Adam

[N2TRUX]

Could it have the wrong length plunger? It sounds like it might not be too long and it's causing the brakes to stay active.

[six5]

AJohn do you have 2 lb residual valves in the braking system?

[Shane]

Residual valves are not needed unless the master cylinder is mounted below the calipers.

[six5]

Do you have residual valves in the system left over from the drum brake system was my point.....

[fixit-p]

It sounds to me like something could be binding or possibly weak or missing return spring if the spring is intact and fully retracted (extension spring) it could be that your push rod is too long also when you bench bled the master cyl did you notice any binding or did it feel rough

[AJohn6]

Originally Posted by fixit-p

It sounds to me like something could be binding or possibly weak or missing return spring if the spring is intact and fully retracted (extension spring) it could be that your push rod is too long also when you bench bled the master cyl did you notice any binding or did it feel rough

fixit-p
I believe my pushrods' length from the pedal to the booster is ok. It is at full extension from the booster. When i bench bled it I didn't feel any thing wrong with it.

Originally Posted by six5

Do you have residual valves in the system left over from the drum brake system was my point.....

six5
I am not sure what a residual valve is.

Originally Posted by N2TRUX

Could it have the wrong length plunger? It sounds like it might not be too long and it's causing the brakes to stay active.

N2TRUX could you please explain what you said with a bit more detail


Thanks again all,
Adam

[fixit-p]

[QUOTE=AJohn6;3228718]fixit-p
I believe my pushrods' length from the pedal to the booster is ok. It is at full extension from the booster. When i bench bled it I didn't feel any thing wrong with it.


How did the spring look next to the push rod under the dash is there any slop when you play with the end play on the brake pedal. The residule valve is just a low pressure check valve down stream of the master cyl. if lifting the pedal helps with your problem than I think that would eliminate anything downstream.

[AJohn6]

When I replaced the old non-power unit w/ the new one there was no spring one it.

Adam

[fixit-p]

That could be the problem here's a pic of my spring just above the push rod

[AJohn6]

fixit-p,

First of all, thank you for getting the picture of it so quick. I looked under the dash and I do have the spring. Just to see if the pedal could come back, I pulled it. It came back a 1/4". I then pressed in on the brake several more times to see if it came back all the way and it did every time. Not even a bit of hesitation. I unhooked the pushrod from the pedal to see if the pedal was sticking and it wasn't. It moves freely and I lubed it when I put in the new booster/MC. The spring has plenty of pressure pulling it up, and the spring looks new.

Thanks again,
Adam

[AJohn6]

bump

[fixit-p]

Have you tried shortening your push rod it may be that at that last 1/4" or so there is not enough spring pressure to release it that last little bit. Its a pretty short lever from where the pedal pivots to the spring mount and that can be offset by the weight of the pedal it's self.

[AJohn6]

Thanks fixit-p, I wil give that a try.

Adam

[62LS1]

It appears you switched from manual brakes to power brakes. I believe the pushrod needs adjusting to make up for the difference in lengths. Also, are there two holes in the brake pedal arm. I'm thinking one is for power brakes, the other for manual.

[chevydog66]

What prop. valve are you using? Do you have a prop. valve for disc/disc?

[AJohn6]

Originally Posted by 62LS1

It appears you switched from manual brakes to power brakes. I believe the pushrod needs adjusting to make up for the difference in lengths. Also, are there two holes in the brake pedal arm. I'm thinking one is for power brakes, the other for manual.

You are correct, I did switch from manual to power. I had to drill a new hole for the pushrod attachment point.

Originally Posted by chevydog66

What prop. valve are you using? Do you have a prop. valve for disc/disc?

I am using the prop. valve supplied with the MC/booster combo. I drove the truck yesterday and the pedal sticking was intermitent. Sometimes it would come all the way back other times it wouldn't. Not much rhyme or reason to when it would happen. I have noticed a slight bit of fluid coming down where the MC bolts to the booster. Could the piston or whatever it is that goes back and forth in the MC be sticking? Is there a rebuild kit for the internals of the MC?

Fellas I greatly appreciate the help I am getting on this problem. One of these days we will get to the bottom of it.

Adam

[fixit-p]

I would say your leakage between the mc and booster is an indication of binding or possily the seal has rolled

[AJohn6]

fixit-p, thats what I am thinking as well. I am going to try to replace that in a day or two if I can and hopefully that will solve this issue. Thanks for the help.

Adam