Brake woes

[bob8619]

1968 C10, drum brakes all around and theyre not power brakes brakes.

I've been having major issues with trying to get my brake pedal to firm up. Bled the system 5 times with 4 quarts of fluid but no fix. I noticed the fluid level in the reservoir for the rear brakes was slowly dropping so I looked everything over many many times but I find no leaks.

I started suspecting the master cylinder so upon closer inspection I noticed that the fluid in the front brake reservoir level goes up, as if the rear fluid is being forced into the front reservoir. I figured this was a master cylinder issue so I replaced it. Bench bled the master, installed it and have a rock solid brake pedal. Hooked up the front brakes only and bled them, less solid but not spongy by any means. Hooked up the rear brakes and bled them and mushy pedal again. Then I noticed the reservoir levels are doing it again, lower in the rear, higher in the front. This only seems to happen when they are both connected to the brake lines, when the rear brake lines were disconnected the fluid level doesn't budge.

There is a proportioning valve in there, could that be letting fluid feed into the front reservoir?

[bob8619]

ACtually I just disconnected the front brake line from the master. I press the brakes and fluid shoots out of that disconnected line. I am assuming that the proportioning valve should not allow fluid to be forced out the opposite side of it am I right?

[Droff]

I don't have an answer to your questions, just wanted to make sure you knew that drum/drum setups run a distribution block, not a prop valve. Learned that myself a few months ago when working on my brakes.
You don't have too many parts left to troubleshoot so it may be the distro block.
Good luck

[bob8619]

Originally Posted by Droff

I don't have an answer to your questions, just wanted to make sure you knew that drum/drum setups run a distribution block, not a prop valve. Learned that myself a few months ago when working on my brakes.
You don't have too many parts left to troubleshoot so it may be the distro block.
Good luck

Yeah I discovered that too after I posted this. It seems as though I don't even need it in there.

[demian5]

Originally Posted by bob8619

I noticed the fluid level in the reservoir for the rear brakes was slowly dropping so I looked everything over many many times but I find no leaks....

I started suspecting the master cylinder so upon closer inspection I noticed that the fluid in the front brake reservoir level goes up, as if the rear fluid is being forced into the front reservoir.

Change the master. Its bad and bypassing internally. I just went through the same thing.

bench bleed the crap out of it but don't push all the way down when bleeding it. Go about half way for a while till all the air (well, most of it) is out.

When you swap out the master, after you hook it all up, open all of the bleeders and let them gravity bleed (with the cap off of the master) for a bit till fluid is running out before bleeding them with a helper.

Sometimes you gotta pump pump pump hold and open the bleeder to force crap out, but most of the time you can just open > press > hold > close.




AND the reason why it moves from one reservoir to the other while connected, and doesn't while disconnected, when connected, it builds pressure and internally bypasses, when disconnected, there is no pressure.

[bob8619]

I eliminated the distribution block and bench bled the master again. Then hooked up the lines and gravity bled and then bled with a helper. Right rear, left rear, right front, left front. All of my shoes are new and adjusted til they are just rubbing the drum. Pedal still feels spongy to me, I have to give it a ton of pedal to just barely slow down and I couldn't lock the brakes up if my life depended on it. Thankyfully the reservoirs in the master are not dropping nor rising anymore.

Do you think theres just air in the lines thats being stubborn or what?

[LockDoc]

Originally Posted by bob8619

I eliminated the distribution block and bench bled the master again. Then hooked up the lines and gravity bled and then bled with a helper. Right rear, left rear, right front, left front. All of my shoes are new and adjusted til they are just rubbing the drum. Pedal still feels spongy to me, I have to give it a ton of pedal to just barely slow down and I couldn't lock the brakes up if my life depended on it. Thankyfully the reservoirs in the master are not dropping nor rising anymore.

Do you think theres just air in the lines thats being stubborn or what?

-
On the drum brakes, one thing I found on mine is when you put everything back together and adjust the brake shoes you can’t just adjust them out until they start rubbing and quit. You have to adjust them out as far as they will go and you cannot turn the wheel or drum at all. This centers the whole assembly in the drum. (I even tap around the drum as I tighten them to help them center themselves) Then you back them off until the wheel/drum just turns, and stop. If you only adjust them out until they start rubbing and quit, the first time you press on the brake pedal the brake shoe assemblies will center themselves and you will have too much clearance between the shoes and the brake drum. I also put three lug nuts on backwards to hold the drum tight against the axle on the rear when adjusting them.

I know it is a pain in the butt to try and hold the self adjusters off of the adjuster wheel while you back them off, but this is the only way I could get my drum brake shoes adjusted correctly.

Putting the vehicle in reverse and backing up while pumping the brakes will cause the automatic adjusters to activate with each pump of the pedal. The problem is if the shoes are not adjusted out as much as possible to start with, it will take a lot of backing and pumping to get them adjusted all the way out.

LockDoc

[bbrriiaann1973]

I know you don't want to hear this but just find a disc brake conversion kit and be done