Proportioning Valve Problems

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Skully

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Hi i took my 68 barracuda out for a ride today the brakes felt real strange hard as a rock brought it home and the back brakes were smokin needless to say they were lockin up,any way i bled them out no help i finally just release the press :roll: ure off them by cracking the rear bleeders, got it to roll, can some one tell me were i can find a factory proportioning valve or a after market valve that will work any ideas will sure be a great help,Thanks for any input
 
B4 I went after a porportioning valve I would check a few other things.as a rule porportioning valves distribute fluid/pressure thru fixed orifices and very very rarely give any probs like this. More likely it is something to do with the master cylinder not releasing the rears or the rubber hose to the rear internally balloning and not letting the fluid return into the system. I have seen more hoses keep pressure on a brake than stuck calipers, porportioning valves,pinched lines, (have you jacked the car up and maybe pinched a line,)

way to test is go drive car and start cracking lines all the way back to the master when yo quit finding pressure go back to the last place you did and you found the problem
 
You know yer probably rite as long as ive been driving ive never had a proportioning valve go bad. and that rear rubber brake line goin to the differential is the one line i never replaced sure it's been on there sinse 68 lol,hey thanks for helping me out
 
I'm resurrecting this old thread because I cranked up the car the other day and it is doing exactly what the OP described here. I've done the same thing as far as bleeding the pressure off. Before I do anything with the car I would love to hear some opinions as to what you guys think might be maintaining the pressure on the rear brakes.
 
Skully said:
You know yer probably rite as long as ive been driving ive never had a proportioning valve go bad. and that rear rubber brake line goin to the differential is the one line i never replaced sure it's been on there sinse 68 lol,hey thanks for helping me out
Click to expand...

A bunch of those rear brake lines are 40+ years old. People never check them. Changing it would be a good thing even if your brakes were working fine.

And changing may just solve your problem.

Could be a win win situation.
 
1968FormulaS340 said:
A bunch of those rear brake lines are 40+ years old. People never check them. Changing it would be a good thing even if your brakes were working fine.

And changing may just solve your problem.

Could be a win win situation.
Click to expand...

It got a new one back in `05-ish but most of this "new" stuff is not worth dirt, so it may have already lived its life.
 
Some may have a residual pressure valve in the master cylinder. I've never witness a failure in those but anything is possible.
Frozen park brake cables are much more common.
The strangest fault I've ever seen was severe steps worn into the touch pads in backing plates. Brakes worked fine until the linings wore down enough to allow the shoe to drop behind that step.
In fact I've heard tales of flex fluid lines plugging but first time I witnessed this was about 2 weeks ago. 99 Town and Country, right front hose. I had automatically assumed frozen caliper. When I broke the banjo bolt loose at the caliper I automatically had a new diagnosis ( squirt ) LOL. For the sake of knowing I had my daughter get inside and try to push fluid out that disconnected hose. I got what resembled tears for fluid flow. Disconnected its other end from the hard line and the reservoir drained.
I added that to suggest the diagnosis procedure. Try to turn the drums by hand, break the fluid circuit, try to turn the drums again. Good luck
 
73hcode said:
I have a 93 Toyota truck doing the same thing could it be the brake booster?
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Probably not, but why not check that possibility? Just disconnect the vacuum source and plug the tube (so no leak to manifold). Without vacuum, it should add no force to the brake rod, just what your foot applies.

In my experience, grabbing rear drum brakes are usually due to leaking fluid on the shoes, either brake fluid or gear lube. However, that isn't the OP's problem.
 
Today I replaced the rear brake hose and PROBLEM SOLVED. The hose on the car(which was replaced around 2005) was blocked. Upon removal I was just able to get air to go through it. After repeatedly trying to clear the line with compressed air eventually no air would pass through it. It definitely had to go. I don't drive the car near enough and it stays outside all the time. I think the combination of inactivity and moisture took its toll on it. I wonder if I cooked the springs enough to lose their temper? Anyway, thanks everyone for your advice.
 
Very good :)
I don't think there is anything we do or don't do that causes the interior of these hoses to collapse. Just lack of real rubber from real rubber trees in the material make up.
The heat is in the drum and will wick to lug studs but little to no wicking to the shoe or springs. Glued linings could come apart though. How much heat required to cause seperation goes to the quality of the glue. Riveted linings wont separate completely like glued but would crack and come apart in pieces. well... Old school asbestos linings anyway. Who know what these modern composite linings might do.
I wouldn't worry about these things unless I had used the very least expensive parts the Chinaman had made.
 
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