I recently did front and rear brakes. Also changed calipers, wheel cylinders, prop valve and master cylinder and bled all the brakes.

I got the back brakes set, then I pump the brake, and the driver side is locked up. The passenger side spins as it should. I readjust it and then I pump the brake and its locked again.


Seems weird, any help?

 

Since the right rear is good, I don't think yer prop valve is plugged. Obviously, something is not allowing the brake fluid to return on the left rear - and the fact that you could bleed both rears shows that fluid is getting there and returning.

Could it be the top brake shoe return spring is in the wrong position/broke/loose? I would check all the springs again and make sure the wheel cylinder dealies that go into the shoes are seated all the way in - toward the wheel cylinder.

After those are set, beat on the shoes (side to side motion) with the heel of your hands to center them. Are the shoes resting on the raised nubs on the backing plate?

 

Never experienced but have heard of old brake lines collapsing as pressure is let off, effectively trapping the fluid and jamming the brakes on. Might disconnect the brake line and see if the brake unjams - if it does, it's easier to replace the flexible line than to tear it apart again. If not, well, the worst that can happen is needing to bleed again and you are going to do that anyway.

 

I would look at your adjuster. As far as I know, or was told a million years ago, your adjuster should only move when in reverse. Back it off, have someone press the brake pedal and see if it moves. If so, something is not right and you will need to take it apart and find the problem.

 

Truck has to be moving for a self-adjuster to operate even if installed backwards etc and they only move a smidge as required.

It does kinda sound by the description that there is a partially blocked line, or hose acting as a type of check valve.

 

I've definitely had the rubber brake hoses collapse internally and cause the problem you describe as the others are describing here.

 

Well it was good for a bit. And I was able to drive the truck about 250miles or so. I took it out and I heard a rotational scraping noise. I jack the back up and I spin the tire. It spins free for about 1/2 rotation then it locks up, I spin it the other way and it seems to lock up in the same place. And it does it on both the driver and passenger side.

To get it fixed the last time, I had the drums turned because I had no adjustment at the adjuster. It was turned all the way in. After turning I had an adjustment.

I looked at all the lines and such and they look good. But I'm starting to think maybe its my parking brake cable or something. Again any help is appreciated.

 

I would think if the parking brake cable was holding the brakes you wouldn't be able to turn the tires at all....could be mistaken, though.

Did you try to loosen up the parking brake as much as you can and then try to turn the tires? I'm afraid you'll have to pull the drums again and pull the parking brake cable to see if anything moves....after loosening up the P brake.

Pictures would help.

 

Just weird how it is in just 1 spot and its both sides. I will take look this weekend and snap some pictures.

 

Did you get the primary and secondary shoes mixed up? I did once on my '65 Mustang and it took hours to figure out.

If they're right, I'd go with bad hoses also

 

Well, this weekend I jacked up the back end. I loosened the driver wheel and I spun it, and It spun free. I tightened it back up, and it locked up again. So I loosened it and tightened it slowly, and it spins free. I drove it and it still makes the noise. It started raining yesterday so I wasnt able to take it back apart.

I will look more into it this week. Definetally seems weird. And when I tightened it, it was locking up in the same spot as before.

 

Locking up in the same spot implies that the drum is slightly out of round. It only takes a few thousandths of an inch to lock it up since the shoes sweep such a large area.

You could have the drums turned to try to eliminate the out of round but I don't know how accurate the shops machine will be and you may still have the issue.

I'm wondering if there is a way to test the bad hose theory. If they are acting like check valves, maybe they will slowly bleed off and allow the shoes to retract. You could duplicate the binding then just let it sit over night and see if the wheel turns the next day. If it does, replace the hoses.

 

As I said, I have never experienced it personally, but I would think if the line was collapsed you would be able to see it on the outside of the hose. Also, if the line was not visually collapsed but the brakes were locked up, you would think opening the bleeder would allow the line to open up. (I am thinking you should have to re-bleed at that point, and once you seal and bleed the system you should probably have a recurrence of the issue.) If by backing off the adjustment you just get some scraping, it would sound more like your adjustment is off, or your shoes or hubs are out of round - if the hose is acting as a check valve I am thinking you would eventually get back to locked up again. Again, I am just spitballing...

 

Hoses can rot from the inside, there's nothing obvious about it from looking at them, and if they are original or 20 years+ they should be replaced anyhoo. They start to slough off and a "flap" will form acting like a check valve.

 

So have I. As it was describe to me by someone who knows (I don't). the hoses fail inside and the lining flakes off. When you apply pressure the shoes / pucks expand and grip the drums / rotors but when you release the pedal there isn't much pressure to back the shoes / pucks off and the liner inside the hose acts like a one way valve, blocking fluid flow.

Replace the hoses (I did). cured the issue.