Locking Fr. disc brakes 69 Camaro

[ken]

I own a 1969 Camaro with factory dics brakes in the front.  The problem is, when driving the car, the front brakes start to lock up
causing a great deal of resistance on the motor.  I have rebuilt the calipers, swapped out proportioning valves, Vaccume boost,
but it still wants to lock up.  I am restoring the car now, so it is not running.  I just rebuilt the front end, in doing so, I also replaced
the brake hoses.  I have heard that this could be the problem.  I will also replace the rear as well.  Any one ever had this problem
before?  Any help will do! Thanks.

[camaromikey]

brake hoses rot from the inside out and that could be the cause of your problem. when they go bad, it traps the fluid in the caliper keeping them depressed.

[Jonesy]

Yep, the inside rots and acts like a check valve. Lets the fluid go to the caliper, but wont release it causing the caliper to lock.
I had this happen years ago and replaced the front hoses and no more problem. I had the calipers rebuilt and master cylinder before I figured out the hoses were bad.

[Steve68]

From Ken's original post:

I also replaced the brake hoses.

[ken]

Thanks!

[NED]

Also check the length of the rod between booster and master cylinder. The master cylinder should seat on the booster without having to push it down. If that is not the case, the rod may have to be shortened some, otherwise the brake master cylinder will not retract fully and the master cylinder will keep pressure on the brakes. When a booster diaphram is replaced, there may be a slight variation in the seat where the rod is inserted causing this situation. 

[69 Z11]

Here's another thing for you to check (happened to me!)  Get under the dash and see if something has gotten in the way of the pedal shaft and is preventing it from returning all the way.  It doesn't take very much, just a couple of wires.  On mine, they were between the rubber bumper and the pedal shaft.   If the pedal can't release all the way, pressure gradually builds up each time you press the brakes.  The pressure won't bleed off because the cylinder isn't retracting fully. 

[jeff68]

Has anything ever been done to the master cylinder?  Could it be possible that the residual pressure valve (RPV) in the MC outlet for the rear drums is not there or not working properly?  Just a thought. 
For more info on the RPVs, check out:  http://www.camaros.org/forum/index.php?topic=2938.0

[ken]

Thanks for all the info, I will go through the break system as recomended.  I still have to get the motor and transmission in,
and get the thing to roll a bit.  Fine tune it from there.  I've got a lot of work to do yet, on the car, but will keep you posted
on the progress of the car.  CRG is the most informitive site out there for us Camaro folks, look forward to posting some more
questions on my car!