Brake Saga OVER!!... see Page 4 (new drop-line installed)

[garydan]

So here is some background. I finished up the 14-bolt install with disc brake conversion, I installed my brake lines...etc. In the process of doing that, the master cylinder ran dry for the rear reservoir. I decided this morning to take the truck to a shop to have them give the lines a once-over and bleed/flush the system.

So after $96 (I despise taking my truck to get molested at these places), I'm told that my "proportioning valve" was blocked and wasn't letting fluid to the rear lines. They said that they reset the plunger thing that might have been stuck in one position after draining the rear reservoir. That "plunger thing" moved freely, but there was still no fluid getting to the rear "It was just dripping out" where the fluid was pouring out the front.

But... when I cut the rear brake line, the fluid ran out just fine for me (which is why the reservoir went dry)... so WTF???

They disconnected the fittings from the master cylinder and the lines at the proportioning valve to make sure fluid was getting to it and it was, it just wasn't coming out of the valve to the rear brakes... Here is a picture of what I'm talking about:

So what's next for me? Do I trust their diagnosis? Is this a typical problem? I never trust these guys, but I just thought they could do a better job with better equipment on bleeding the brake system.

 

[Stomis]

Bleed it closest wheel to farthest when a system ran completely dry.

 

[odin]

What youre describing is normal.
When you run the rear of the braking system dry the "plunger thing" is actually a safety check valve to keep the truck from losing All braking, if there is a failure at the rear of the system.
Usually you can reset it by pushing it in.
Not all the time though.

 

[garydan]

Well I opened the bleeders in the rear, and I have fluid coming out. I'm waiting for my wife to come home and pump the brakes. I wonder if the plunger reset itself on the way home from getting screwed at the shop?

 

[xCaliK5x]

I had the same problem with mine. I got some fluid out of the rear, but the rear brakes weren't working. The kid that had the truck before me and did the axle swap didn't bleed them right and never knew. I found out when I put it on a dyno and coulnd't get the rear wheels stopped! I used a power bleeder and opened all four bleeders so the pressure would be equal in the prop. valve and pumped the brakes and it reset right then and there. (you should have the red "BRAKE" light lit up on the dash if there is a malfunction, mine was burnt out!)

 

[garydan]

I had the same problem with mine. I got some fluid out of the rear, but the rear brakes weren't working. The kid that had the truck before me and did the axle swap didn't bleed them right and never knew. I found out when I put it on a dyno and coulnd't get the rear wheels stopped! I used a power bleeder and opened all four bleeders so the pressure would be equal in the prop. valve and pumped the brakes and it reset right then and there. (you should have the red "BRAKE" light lit up on the dash if there is a malfunction, mine was burnt out!)

I think that is my problem. Can you also push on a plunger (on the left in the pic above) to reset it?

 

[xCaliK5x]

I tried a little, I didn't want to get too rough with it though and had to bleed/flush my brakes anyway. I figured if it worked on a pressure differential, technically it should recenter once equal pressure is on both sides. Which is good since I didn't want to F&*# with changing it. If you open just the rears and pump the brakes to bleed them, its going to do its job and slide over to block off the rear circuit. If you can't get the button thing to move, what I did worked great, I have the key on and watched the BRAKE light go out. For being simple, these trucks sure can be a PIA sometimes. Best of luck.

 

[garydan]

I tried a little, I didn't want to get too rough with it though and had to bleed/flush my brakes anyway. I figured if it worked on a pressure differential, technically it should recenter once equal pressure is on both sides. Which is good since I didn't want to F&*# with changing it. If you open just the rears and pump the brakes to bleed them, its going to do its job and slide over to block off the rear circuit. If you can't get the button thing to move, what I did worked great, I have the key on and watched the BRAKE light go out. For being simple, these trucks sure can be a PIA sometimes. Best of luck.

Thank you for the information! I'll try this out tomorrow night after work. Do the combo/prop valves in our trucks function differently than more modern vehicles that a typical grease monkey (no offense to grease monkeys here ) would be more accustomed to?

 

[xCaliK5x]

I'm unsure if they have a bias front/rear or they are just there as a safety valve/warning lamp to sense a pressure loss. Which makes no sense since the master is a dual circuit and has basically two reservoirs in one, the only thing it may do is trigger the light so you know?

 

[odin]

I'm unsure if they have a bias front/rear or they are just there as a safety valve/warning lamp to sense a pressure loss. Which makes no sense since the master is a dual circuit and has basically two reservoirs in one, the only thing it may do is trigger the light so you know?

Two reserviors yes.
But they both go through the valve...so a complete loss of braking is possible without this safety feature.

 

[garydan]

Well I tried some of the suggestions in this thread so far. I opened the bleeders on the front and stomped on the brakes to try and reset the proportioning valve. I'm not sure if it made a difference. Here is a shot of the "Button" as it sits now:

Is this how the "button" is supposed to look like? I tried pushing in the button with my hand and it won't budge. I bought a MityVac vacuum bleeder and hooked it up to the right rear. I get bubbles and a little fluid but that's all. If I have someone hit the brakes I barely see movement in the fluid line within the tube.

What do I do next?

 

[garydan]

ttt... need feedback on the prop valve, whether or not it looks like it needs a reset.

 

[Stomis]

I would say get a new one either way since theres suppose to be a protective boot on there. Perhaps when the brakes went out of balance some corrosion was taken in and locked it up?

And its simply really. You push that button, if it goes in then it need to be reset, if it doesnt then your problem is either else wear or your valve is frozen.

As said you should get a brake light if its plugging up the rears.

 

[garydan]

I would say get a new one either way since theres suppose to be a protective boot on there. Perhaps when the brakes went out of balance some corrosion was taken in and locked it up?

And its simply really. You push that button, if it goes in then it need to be reset, if it doesnt then your problem is either else wear or your valve is frozen.

As said you should get a brake light if its plugging up the rears.

Well there was a rubber cap on it, I removed it for the picture. When you say "push the button" what do you push? The pin, what surrounds the pin, or both? I pushed in on the whole thing and it won't budge. Do I just need to use more force (hammer)? Do I need to open the front bleeders and then try to push it? Does the button even look like it needs to be pushed in? I don't know what it looks like normally. I never got a brake light on, even when I drove the truck with the rear brakes open. So I'm assuming the light was blown.

 

[cegusman]

Push in the small pin.

 

[garydan]

Well I kinda of feel like an idiot now. If its the stupid pin I didn't even try pressing that in. Everything else I've read about this had me thinking I had to push what surrounded the pin. If the pin "housing" is fixed that would explain why I couldn't push it in... LOL

 

[Stomis]

I couldnt tell you since the only time I had to push my the rubber was on. it kinda seemed like there was only one way to push it, and it was VERY easy. Not tools, hammer, nothing. You may need to replace it, sounds frozen.

 

[garydan]

Keep in mind, I'm no engineer. But if I read this diagram correctly. I should be able to "reset" the rear brake valve stem by holding in the pin and hitting the brakes.

 

[496truck]

When I got my truck the rear lines were rusted out and the half of the master was empty. After replacing the lines and one wheel cyl I could not get it to bleed properly. I bought a Mityvac as well and it would just pull bubbles and small amounts of fluid. I found that putting some thread sealer on the threads of the bleeder screws prevented air from seeping past and I was able to vac bleed the brakes. After getting fluid out to the rear (and closing the bleeders) I was able to pedal push the prop valve back into place automatically, and the light went out. At this point I was able to pedal push bleed the brakes with a helper.

The point of the proprtioning valve is two fold...
1. It inhibits front brake pressure untill a certain rear pressure is reached, thus balancing the front/rear braking action. Without the valve, the front brakes would lock up before the rear even has enough pressure to activate.
2. When pressure in one side (F/R) is lost the plunger slides over to ground a switch which turns the light on, notifying the driver that something is wrong. The valve, although one piece, is sealed between the front/rear brake fluid systems. If the fluid is lost on one side it does not effect the other.

 

[ChrisPerry]

I found an article somewhere that said if you pump the brakes up real hard, and have a helper crack a front bleeder that it will trip the combo valve forward. They said that the little button will then reset the valve correctly. Something about the reset button only being able to move the piston one way. Kinda makes sense to me.