Sticky front brakes

[BlueOvalDave]

New member to this site
Already converted my daughters 67-F100 to P.S and pwr disc with the info I gathered from this site
used the original booster which is good but replaced all the other stuff, calipers, hoses and M/C. Brakes bleed up fine but the front calipers seem to stick, this can be relieved by lifting up on the brake pedal or it will relieve itself within 5-10 seconds after depressing the pedal. Calipers check out O.K., i have replaced the proportioning valve with a known good unit, all mechanical linkage and pivot points are not binding and the booster to M/C rod measures out correctly. Even replaced the M/C to eliminate it as a potential problem and I'm using decent reman stuff from Napa. I'm wondering if there is aresidual pressure check valve in the M/C for the front disc's, I know that they're sometimes used in the port for the rears. Anyone have any input or thoughts?

[SteveC]

is this a master cylender for drum fronts or disks. Couldnt tell from the info you had gave.

[BlueOvalDave]

The master is for a disc set up

[flyboy2610]

Do you know if both sides are sticking or just one?
You may have a brake hose that is split internally, and that can act like a check valve and not release the brake pressure like it should.

[fordman]

if its not line blockage or a collaping brake hose then it could be a bad caiper piston not wanting to return properly.

[fmartin_gila1]

Do you have the MC hooked up properly? If wrong, you may have a residual valve in the disk circuit and none in the drum circuit.

Fred

[BlueOvalDave]

New hoses, calipers. Checked calipers to make sure they were'nt sticking. And both sides are doing it.
I had the bad hose experience on an escort, that had me scratching my head .
Thanks for all the responses, I'm gonna drive it to see if it improves.

[two-bit]

Following your post here and i ran into a similar problem on a brand X truck.
Turned out to be a vacuum problem with the booster.
The booster wouldn't release correctly. I don't remember if it was a vacuum feed issue or a issue in the booster.
(It was over 15 years ago )

The reason i bring up the booster is because its the only thing you haven't replaced.
Try the brakes with the booster hose unhooked. ie: booster able to breath with no restrictions.
It could be possible that somehow the booster is not able to "breathe" correctly on release and it is holding the master cylinder rod "in" . Have you checked the rear brakes to see if they are releasing correctly?
You also said if you pull up on the pedal it goes away, if you give it some time, it will eventually release back to the full release position. That seems like a vacuum hold from the booster.

With the brand X truck, we just put a different one on and the problem went away. I know that isn't the easiest thing to do with a '67.Being a one year only part.
I'm not sure how to test a booster correctly, maybe some here does, maybe you already have and found it OK.
Just sounds like a physical restriction in the process of releasing the piston in the master cylinder.

Good luck with it. Hope you find the problem.
Let us know if you figure it out, it always good to know the right answer for future reference

Two-bit

[BlueOvalDave]

I took the booster out of the equation and it still does it . Thats one of the first things I looked at, I was thinking along your line of reasoning, in fact almost hoping it WAS the booster. Man, I've done my share of brakes in my time including BIG trucks and this has got me When I git home from work today the ol' girl is gettin a WORKOUT When I do get it figgered out I'll be sure to post.

Thanks and later,
Dave

[Billiam68]

I had similar issues with my F250 front disc brakes. I replaced the bolts, springs and bushing that hold the calipar to the braket, made a huge difference.

Good luck,
Bill

[Thunderfoot]

You say the brakes release if you lift up on the brake pedal, this to me would be the problem...
The brake pedal must be binding up somewhere that it is not returning all the way with ease. Or, the other was the booster as two-bit mentioned, but just unhooking the vacuum hose to it probably wont help with the diagnosis. If the booster has a restriction on returning back to its off position it could still have this problem without the vacuum hooked up.
But it doesn't sound like anythings wrong with any of the hydraulic parts of the brakes or the MC, as the connection from the MC to the booster floats (is not directly connected) so pulling back on the pedal will not pull back the MC. Something is not letting the booster or brake pedal to come back smoothly to release the MC pressure.