So i had a leaking rear wheel cylinder, upon inspection the shoes were also worn and the drums were out of spec. I bought all new cylinders, shoes, hardware and drums. Thankfully the mother in law works for O'reilly's auto parts. I replaced everything, Nothing was binding, everything seems fine. Bled the brakes, and test drove the vehicle around the neighborhood with no problems.

After driving to work the next day, about 25 miles, still seemed to be fine. Then about 5 miles into the drive home, something started to drag. The rear brakes were locking up. Later on the drive home, they released. I'd stopped a couple times to make sure they weren't cooking. Pulling and releasing the parking brake seems to have released them. Took them apart when I got home and the parking cable on the driver side was out of position. Fixed this and seemed to solve problem. Untill drive to work next day. same thing. Toyota buddy of mine at work is stumped too. So we re-bled the brakes after work. All was good again. There was a little air still in the lines. Drove the 25 miles home and no problems. But, on the way into work this morning low and behold they started to lock up again.

All we can think of is maybe one of the wheel cylinders is bad. Any other suggestions or information would be greatly appreciated. Sorry for the long winded post. Thanks.

 

I had a similar issue , they wud start to drag to the point the truck almost stalled..it was the master cylinder for me

 

it would not be uncommon for you to have a defective wheel cylinder. if they are under the "defective warranty" stage, replace them. since those rear components were the only things that ad changed with the new issue, i would start there.

also, make sure that all contact points between the shoes and backing plates have a spot of grease on them to help free up their motion.

 

is this a 4wd or 2wd?

 

Yea, I'm getting 2 new wheel cylinders today. I cleared out all the rear lines and replaced the old rubber hose from the chassis to the axle and still doing it, so changing out the cylinders tonight.

It's a 2wd.

 

you arnt adjusting the rear shoes too tight right? ive seen people clamp em down and later on down the road they lock up.

 

nope, I've adjusted them several times, but the wheels have always been able to still be turned by hand.

Do these 2wd trucks commonly have a brake proportioning valve? If so, I don't see it listed at the auto parts stores websites. Could this be causing the problem and if so where do I get one?

 

do they freespin when you turn them by hand or do they drag and stop when you let go of them. you should be able to spin em by hand and have them spin around once or twice with out you touching them. if they drag so hard that you have to force them around they are too tight and will lock up.

 

the porportioning valve should be in that combination valve block about a foot or so down the firewall. check the lines and hoses for kinks or rips. also the load leveling valve on the rear axle. also on the backing plate where the brake shoes contact the backing plate, spread a little of anti-seize on there.

 

Ok, the latest piece of advice I got from a long time mechanic was the shoe towards the front of the vehicle is thinner than the one that goes to the rear.

One side the shoes are very close, but there is a difference in thickness of the material. The other side was way closer, but they were possibly switched. Also when I took them apart and switched them the little slots of the adjuster that slide onto the bracket of the shoes went together much smoother. I originally just figured the difficulty was due to excess paint on the bracket.

So far so good on them not locking up, but the real test is when I drive home cause this is when they locked up the first time.

So just checking on here if this is something that is true for our trucks and drum brakes in general. If so, I'll know next time.

 

ya the "smaller" shoe goes up front, usually its not thinner it has a smaller um...diameter of pad. hard to explain easy to show if you had the shoes sitting side by side. Some makes and models ( not our trucks ) the shoes are the exact same, on ours we have front and back shoes.

 

Ok, so after the pad flip problem was fixed it took a lot longer for them to lock up. This time it was only one side though. Had a mechanic adjust them, and for now they seem to get locked up under light peddle pressure. If I push hard on the pedal they seem to release.

My Haynes manual states locking up under light pressure would be because the proportioning valve. I'll try and get a picture of mine posted on here tonight.

 

Ok, new twist. I swear the rear brakes locked up when I did a hard downshift. No brake was applied at the time.

After I unlocked them by opening and closing the wheel cylinder bleeder valve, I tried to replicate this, but when I want them to lock up they wont. Starting to think I need an exorcist.

 

Wen u downshifted were the RPMs high? If so it wasnt the brakes, u chirped the tires. Its happened to me before.

 

Yea I have done that before to go into a slide on purpose. It's like pulling your e brake but using your gears. It's a method some drifters use.

So was it brief or did the brakes completely lock up and stay locked up when you downshifted?

 

This started them locking up. It got worse as I drove on.

I may have found the problem. I double checked the shoes I put on and they are exactly the same front and rear facing shoe. Looked at the pictures I took before I took it apart and there is clearly a difference in the front and rear pad. Waiting for a different set of shoes to come in.

 

Ok, replaced shoes, and re adjusted, still locking up. Bled the pressure out this morning form the rubber hose from the axle and brakes released. Next time they lock up I'm going to the line above the proportioning valve underneath the master cylinder.

I'm still thinking this is the problem, hopefully will get an answer when I do this. If so, I'll need all the help I can get locating one. There is a picture of it under the parts wanted section. I'll post one in here too if that turns out to be the case.

Thanks for all the help and suggestions on this problem.

 

You can delete your proportioning valve completely. And just run a single line to the rear brakes. Then they will be at full braking pressure though. You can also try installing a check valve or also known as a backflow preventer.

 

so loosening the lines on the return side or the output side of the master cylinder released the brakes, so guessing fluid is free flowing through the proportioning valve. Guess the next thing is the master cylinder. Putting a new one on tonight.