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

ChrisPerry said:
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.
Click to expand...

That didn't work for me. My plan of attack for tonight is:

1) Hold the pin in and press on the brakes a few times
2) Wrap some teflon tape around the bleeders and attempt to vacuum bleed again.

.. Then if I'm still not successful... order a new proportion valve and then strip all of the fittings and curse repeatedly.
 
just found this troubleshooting goodness from a brake web site.

Testing of Combination/Proportioning Valve

  1. Using the test light, attach clip to a positive and touch the point of the tester to the electrical connection of the combination valve.
  2. If NO light goes on, the valve system is operating correctly. No further testing is required.
  3. If light goes on, this indicates the pressure differential valve in the combination valve is stuck in front or rear position.
  4. Bleed brake system to determine which system, front or rear is not getting proper flow of fluid; one system will squirt out of the bleeder, and the other will trickle out.
  5. The system with the flow must be opened for the flow to alter the pressure on opposite side of pressure differential valve to center valve.
  6. Slowly depress pedal with steady pressure until light goes out. When light goes out close the bleeder.
  7. Your system is now centered. Bleed complete system.

On edit:
reading through the post it looks like the shuttle in the combination valve is indeed blocking the rear brakes. Sounds like you need to do steps 5 and 6. Step 5/6 tricks the combination valve to think there is a leak in the front system and shuttle off to that side. That will allow you to bleed the rear brakes. I guess the key is SLOWLY depressing the pedal while the front bleeder is open and watching the light.

Hope that helps,

Cheers,

Rufus
 
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Also, looking at garydans combination valve diagram it appears that the "button" only impacts the FRONT brakes. Reading several sites I am seeing a pattern that you only need to push the "button" when bleeding the front brakes.

This makes sense to be as you normally start bleeding a system from the wheel furthest from the master.

You bleed the rears first while the front has no pressure (air in the line). The shuttle will slide over and block the front (setting the "button") still allowing flow to the rear. once the rear is free of air you push in the "button" allowing flow to the front calipers. Since the rears are air free the shuttle will not slide over and block the rear.

Suddenly brake bleeding procedures are making sense to me when using a combination valve system like GM used.

Thanks for posting up the issue as it made me go out and research things.

Cheers,

Rufus
 
Maybe this is why my brake light is on....off and on. Gotta check this out today.
 
Well I worked on it last night for a while. I held the pin aka "button" in and pressed on the front brakes with the bleeders open a few times. I hooked up the vacuum bleeder to the rear with teflon tape on the threads. It was pulling a vacuum so there must be a decent blockage somewhere. I still got no real flow of fluid. It looked promising at first.. but I was shot down real quick.

Tonight I'm going to do some electrical testing to see if that valve is stuck and its not some other blockage in the line somewhere. It's looking more like a new proportioning valve for me....

Looking at that diagram again, I don't see how the pin aka "button" does anything with resetting the valve to get fluid flowing to the rear again.
 
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Try opening both rear bleeder screws, filling the master and letting it gravity bleed...for a while.

If not, maybe you can rent a pressure bleeder from a local auto parts store.
 
Have you tried to bleed the valve itself? Try bleeding each line where it connects to the valve just as you would at each caliper. If there is any air in the valve, it will be forced out towards the calipers.
 
Today I decided to disconnect the drop line from the bracket. Fluid began to pour out and the master cylinder started to empty. So its not the proportioning valve!!

It looks like for one reason or another fluid isn't getting through the drop-line. Right now I have an open tee to see if it gravity bleeds and fluid starts coming out. It's been sitting there for over 30 minutes yet I still see no fluid. I hooked up the vacuum pump to it and it builds up a vacuum and I get no fluid.

Could the drop-line be blocked somehow? How can I fix this, any ideas? Do I need a new line? These are brand spanking new ORD lines.

Here is a picture of it pulling a vacuum without any fluid (the hard line is now hanging down I removed it from the truck but its still hooked up at the fitting near the passenger door)

small_DSC07352.JPG
 
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I know this sounds stupid, but was there any kind of plug in the drop line before you installed it? Maybe something broke off.
Basically, if you disconnect both ends of the drop line and cannot suck air through it, then the line is stopped up by something. Its not too uncommon for an old flex line to have the liner fail and let a strip of it come loose at one end and act as a check valve. Never saw it in a new line before. Try taking the other end loose and suck from that side. Maybe it will get something out.
Otherwise, use air pressure. But be sure to put a rag over the other end so you can see what comes out.

J.
 
I was able to get some little drips out of the drop line using the standard bleeding method (wife hitting brake pedal). The pedal was really tight though. I'm sure it's tight due to whatever is blocking the line. I opened the tee and sprayed some compressed air in the end. The air barely came out the other end. I put a balloon on the end of the line to see if any air was getting through. There was very little air.
 
sounds like an internal layer is collapsed.. is it new?
 
I notice you are in Fl. You did not have that line laying open outside for a day or so did you?
I once took a hard fuel line loose from my genset and left it open while I ran to town for a part. Gone about 45 minutes. When I got back, a dirt dauber was already starting a nest in the end of the line.
At my hunting camp in the river swamp, one of the last things we do when we break camp is tape up all the outlets with duct tape. Otherwise they all have to be replaced next winter because you cannot plug anything in due to the dauber nests.

J.
 
Fordum said:
I notice you are in Fl. You did not have that line laying open outside for a day or so did you?
I once took a hard fuel line loose from my genset and left it open while I ran to town for a part. Gone about 45 minutes. When I got back, a dirt dauber was already starting a nest in the end of the line.
At my hunting camp in the river swamp, one of the last things we do when we break camp is tape up all the outlets with duct tape. Otherwise they all have to be replaced next winter because you cannot plug anything in due to the dauber nests.

J.
Click to expand...

Interesting... but no. :D The truck has been in my garage.
 
I HAVE BRAKES!!!! Woo Hooo!!!low

Well after about 2-weeks of frustration I now have working rear disc brakes on my "new" 14-bolt FF axle. I got the new line from ORD today and installed it. What a world of difference. There was definitely some sort of manufacturing defect with the original line (it happens). ORD says they pressure test every line, maybe they should flow test them as well. I put my mouth on the end of both lines and blew. You can tell a major difference in flow.

When I hooked up the lines the fluid was flowing freely. I opened up the bleeders on both ends and had it bled in about 5 minutes. It's amazing how easy this sh!t is when you have non-defective parts!

Moral of the story... blow on your lines before installing :D
 
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