Brake bleed help?

[kdrodworks316]

As many on this board know, I converted to disc brakes on my burb. I used a prop valve from CPP. It has one wire coming out of it, where does it go? I have pumped and pumped and cant build any pressure to bleed the brakes. I have cracked every line from the master down and was able to get fluid, but cant seem to get it at the calipers. I have opened the bleeders and pumped some more, still nothing. anyone got any ideas? this is the only thing keeping me off the road, I am going nutz to drive it.

[64GMCHorsepower]

Did you brake bleed the new master? Do that first, then install the prop valve, then go to bleed the lines.....

It just takes a while....

Your master should have come with instructions on how to bench bleed it...

[joe231]

the wire from the proportioning valve is a pressure differential switch. it grounds that wire if there is a difference between the front and rear circuit ie a leak in one. the wire goes to the ground side of a brake warning light, and the hot side is hot with the key so if the pro valve switch is made it goes to ground completing the circuit and lighting the light, warning you of a leak.
and i second the bench bleeding.
something else you can try is open both front bleeders, take the lid off the master and let it sit. you should, after some time, have gravity bring fluid to the calipers and start dripping then you can pump and bleed. sounds like you have an air lock.
you could even go get you a mity-vac and use it to bleed. it is a one man bleeder
oh and one more thing, get a small container and a piece of clear hose that fits the bleeder, open the bleeder, putt the hose on it, put the other end into the container with clean brake fluid in it so the hose is under the fluid, then you can pump the brakes and the air will flow out when you push the brake pedal down and fluid will be sucked back in when the pedal comes back up
bit long winded, hope it makes sense

[Anthony Fremont]

Originally Posted by 64GMCHorsepower

Did you brake bleed the new master? Do that first, then install the prop valve, then go to bleed the lines.....

It just takes a while....

Your master should have come with instructions on how to bench bleed it...

I put a new master on my truck. Tiny little one bore replacement just like the factory used. I had to pump it over 100 times by hand to bleed all the air out of it. I didn't think I'd ever get done; I though something was wrong.

It came with a plastic plug to block the output while you bleed it. I've done others that came with a section of hose to loop back into the master cylinder reservoir. That type bled out allot faster than the blocking plug type.

[kdrodworks316]

bench bleed done the trick, I still got to go thru the rest of the system, but I am gaining ground. I can stop if I need to, which is better tha when I started today.

[joe231]

[kdrodworks316]

OK, I have the front done, but I cant get any fluid to the rear. I have tried every trick I know, and nothing. The brakes worked great before the disc conversion, so I am sure the rest of the system is sound. I have bled the prop valve and have fluid out of it. I have also cleaned the bleeders on the wheel cylinders. Any ideas?

[Anthony Fremont]

Sounds like you may need to replace the rear hose. Mine was totally blocking fluid from reaching the rear wheel cylinders. New hose, no more problems. Use a good tubing wrench to loosen it or you will regret it.

[joe231]

did you open both rear bleeders and let it sit?

[kdrodworks316]

I havent opened the bleeders and let it sit, think thats the trick? I should add that if I hold my finger over the bleeder hole, and pump the brakes, I can feel pressure and vacume.

[Anthony Fremont]

If you can feel pressure, then it sounds like it is working. I gravity bled mine to flush the system out. It worked real good, just don't let the master cylinder run dry or you'll have to start over. Loosen the cap so that air can get into the MC.

[joe231]

I worked at a national chain auto shop doing mostly brakes and exhaust, I did LOTS of brakes, gravity bleeding made getting all the air out much faster and easier.
give it a shot, what you got to lose except air
you get your grille and bumper mounted?

[kdrodworks316]

Thanks Joe, I will try to gravity bleed in the morning. I got the bumper and the tach in, havent got to the grille yet. I will do that while I gravity bleed. So I just open both bleeders up and wait? how long should this take? I am getting really flustered with this thing, oh and the package for you will go out monday.

[joe231]

yeah just open them both, they should start to drip in 10-15 minutes or less, you can let 'em drip a bit then close them both and bleed as normal starting at the farthest wheel from the master.

cool deal, can't wait for pics
and thanks

[kdrodworks316]

I will snap some pics in the morning for you. Thanks for your help

[joe231]

yeah man
not a problem

[kdrodworks316]

gravity bleed is a no go. It sat all day with the bleeders out and never even made a drop. I have traced the whole system to the rear and have no blocked lines. I got fluid to the coupler at the rear, and to the T fitting, and to the passenger rear, but cant get it to the driver rear. I changed the line to a know good one and still nothing. The pedal felt like it was getting better when trying to bleed till I did the driver rear, then it instantly when to crap, and I never got it back. HELP!

[joe231]

that sucks
have you tried person #1 open the bleeder, person #2 slowly pushed pedal to the floor and holds, person #2 closes bleeder while pedal is on the floor. try it a few times till you get fluid flow
did you get both reservoirs bench bled properly?

also you can try person #1 holds pedal down with all the bleeders closed, person #2 cracks open the fitting at the master for the rears

are the rear shoes adjusted properly?

[Anthony Fremont]

Originally Posted by kdrodworks316

gravity bleed is a no go. It sat all day with the bleeders out and never even made a drop. I have traced the whole system to the rear and have no blocked lines. I got fluid to the coupler at the rear, and to the T fitting, and to the passenger rear, but cant get it to the driver rear. I changed the line to a know good one and still nothing. The pedal felt like it was getting better when trying to bleed till I did the driver rear, then it instantly when to crap, and I never got it back. HELP!

You loosened the cap to the reservoir right? Fluid should literally run thru the system when the bleeders are open and the cap is loose. It won't exactly be a stream, but the drops will be coming quickly.

I still suggest changing the rear hose, it wouldn't take much dirt to stop it up if it's real old. Once I put a new hose on, I had no trouble gravity bleeding the back. In fact it would only take about 20 or 30 minutes to empty the MC with one bleeder open at a time, so I had to keep a close eye on it to avoid getting air in again.

Take your bleeders all the way out and make sure that they aren't plugged up.

[bagged69c10]

I know your pain. I am having a problem with a 69 sub where the pedals go to the floor.

[padresag]

is that an adjustable proportioning valve; perhaps it needs setting
ron

[kdrodworks316]

Ok I feel dumb, I finally put the pressure bleeder on it and still nothing. So I pulled the wheel cylinders out and pulled them apart, plugged up! So I got the brakes bled finally, and now I got to put some shoes on, no problems now. Thanks for all the help guys

[joe231]

i'm happy to hear it.
it is usually something painfully simple

[soba_03]

KD,
Well it looks like you got it worked out. I might add, the porp valve if I remember it correctly actually has a hyd fuse in the valve body. This is intended to be used in the event that you loose a line. It will shut fluid off to which ever bowl has the leak. I was told that in the front of the prop valve the silver looking circle will actually lock out one or both of the bowls from letting any fluid out. Again I have no first hand experience with this only what I was told. However a call to CPP would certainly clear up and misconceptions that I've given you.

How's it stop now?

Also I'm a bit slow going on my project, it would seem that an old knee injury from about 8 years ago has cropped up again and i'm limping around here hoping that it's going to go away like it did some years ago.

Oh yeah I thought of the Irony you working on your burb with a bum knee. Well Bro, I'm right there with ya.

40 in less than a week and the bottom falling out......LOL

Glad to see your back to work on it, I have been off the board for a while just trying to get things ironed out round the house and searching for a good G body Cuttlass or Monte for driver. The 68 is great but I'm getting old and some creature comforts are needed.

Hope all is well... I'll keep ya posted on the knee saga....

Regards....