Brakes

[Omar]

Hello folks...
I just bought a 1981 c10 needs some work, so it's a work In progress. My question is the rear brakes were bad so I went ahead and replaced pads drums,springs and cylinders. Once I had everything installed and started to bleed them using the buddy system. My buddy would pump the the brakes and hold but when I opened the bleeder valve I got nothing??? This went on for several attempts when I finally just had him mash the pedal, and at that point I got fluid. Once i was done we put the wheels back on and did a road test all was fine when i decided to mash my brakes as if it was an emergency, the truck stopped but when I released the pedal my rear brakes stayed locked up? I made it back home but my rear brakes were just a little hot...so my question is what should my next move be to check? Could it be my combination valve sticking? Any help would be appreciated...

 

[78C10BigTen]

My first thought is a bad proportioning valve but im not good with brakes so... im sure more experienced people can help here. Be patient....

 

[78C10BigTen]

Also just a thought that has nothing to do with the fluid but check to make sure your E brake hasnt been engaged in anyway somehow. Starting simple...

 

[Old77]

Not sure why this was posted in the Introduction section but I’ve moved it to the proper area for you

 

[Omar]

Thank you...

 

[75gmck25]

IIRC, you have to manually flip the switch on the proportioning valve when you are bleeding the brakes, so that it provides equal pressure to both front and back systems. The valve should be located on the front driver's side of the truck, up under the left side frame rail or radiator support. You can follow the brake lines down to it.

In failure mode the proportioning valve is designed to switch internally and shift pressure to whichever brake system is still good, so it sends all pressure to the brakes that still hold. This means it may not pressurize the brake you are bleeding (since the valve is open) and you will have trouble getting it to bleed properly.

Bruce

 

[bucket]

I've never had to mess with the prop valve on these trucks when bleeding the brakes. While it may be the technically correct way, it's never been an issue.

Is it for sure both rear brakes hanging up? It could be the rear brake hose is collapsed internally and retaining pressure in the wheel cylinders.

 

[RoryH19]

Unless the prop valve is bad, there is no need to reset the slider to the middle.
I've had to replace one on my K5 as it had been sitting for many years.
Also are you getting a brake light on your dash even if the e-brake is off?
There is a sensor on the prop valve that will trigger the light in the dash if it has gone bad. Also if fluid is only going to front or rear.

 

[4WDKC]

sounds like the flexible line to the rear brakes collapsed and is restricting fluid from returning to the master cylinder. Lift the truck loosen the lines from each wheel to the flexible line on the rear axle then close it. Should be enough pressure release to turn the rear wheels. Replacement lines are inexpensive.

 

[HotRodPC]

My vote is also for a collapser rubber hose just before the T over the axle pumpkin. Can't cost that much and it's time to replace it anyway so it's not a waste to give it a try.

 

[RoryH19]

Right it's $10 - 15 at most local part stores.

 

[Charlie]