Brake problem...frustrated

[clinebarger]

Originally Posted by airbrushguy

Latest report: bled brakes, rear first, pedal hardly went down when opening rear bleeders, pedal did go down when I bled front.
Driver side cylinder was tough to open, then leaked after bleeding. Going to take drum off tomorrow and probably replace the wheel cylinder to stop leaking.
Still wondering why the pedal didn't hardly go down when I opened the rear bleeders???
Thanks
Posted via Mobile Device

At the proportioning valve, Crack open the brake line that goes to the rear while the brake pedal is pressed, If the pedal now goes down like its suppose to...Replace the rear rubber flex hose.

Still the same? Crack the line at the Master Cylinder...If it now goes down....The proportioning valve not centered/stuck/rusted.

Still the same? Bad master, Master not bled, Air in the lines.

[airbrushguy]

Originally Posted by wilbilt

The piston in the combination valve ("proportioning valve") may be off-center and stuck, blocking fluid flow to the rear brakes. Normally, if the piston is offset, bleeding the opposite end (in this case, the front) will cause it to return to a centered position. There may be a lot of crud in the valve causing it to stick.

The fluid came out well from the rear bleeders, it's just that the pedal did not move down much at all while the bleeder was open.
Thanks

[wilbilt]

Originally Posted by airbrushguy

The fluid came out well from the rear bleeders, it's just that the pedal did not move down much at all while the bleeder was open.
Thanks

That sounds strange, as pedal movement=fluid movement. If you open a bleeder, the pedal should go nearly to the floor.

I would do as clinebarger suggested. Start at the master, cracking lines open then move down the line until you find the point of restriction. MC pistons can stick, rubber hoses can swell shut, metal lines can be crushed, etc.

[airbrushguy]

Originally Posted by wilbilt

That sounds strange, as pedal movement=fluid movement. If you open a bleeder, the pedal should go nearly to the floor.

I would do as clinebarger suggested. Start at the master, cracking lines open then move down the line until you find the point of restriction. MC pistons can stick, rubber hoses can swell shut, metal lines can be crushed, etc.

I will go through that tomorrow, but keep in mind that all of that has been replaced...recently.
Thanks

[airbrushguy]

Front bleeding: pedal goes to floor...rear bleeding: pedal does not go down much but fluid does come out. ?????

[OJ1988]

Is fluid running out the rear, or spraying with pressure?
Posted via Mobile Device

[70CHEVYBB]

You have to open a front bleeder and stomp on the brake pedal real hard, The sudden loss of front brake pressure will trip the prop valve. You may have to do this 2 or three times depending on how stuck the valve is.

[bollybib]

Originally Posted by 70CHEVYBB

You have to open a front bleeder and stomp on the brake pedal real hard, The sudden loss of front brake pressure will trip the prop valve. You may have to do this 2 or three times depending on how stuck the valve is.

I did this with mine a bunch of times (trying front, then rear) and the darn thing never did free up.

[airbrushguy]

Originally Posted by bollybib

I did this with mine a bunch of times (trying front, then rear) and the darn thing never did free up.

So what did you do, replace the valve? I have an extra one, should I just replace it?
Posted via Mobile Device

[wilbilt]

Originally Posted by airbrushguy

So what did you do, replace the valve? I have an extra one, should I just replace it?
Posted via Mobile Device

It certainly couldn't hurt to change it if you have an extra. That would eliminate it as a possible source of the problem.

[Steve Hafner]

. . . .

As far as the system not stopping well, I have the same problem with my new booster.

I asked this question a few months ago and got this answer:

. . . .

[OJ1988]

Check pushrod as above.

Also, bleed bleed bleed. When I got my new brakes done, it seemed like I had to bleed forever. I bet I filled the resevoir 6 times or more. Finally the fuild out the rear went from a steady stream, to a pressure blast!
Posted via Mobile Device

[OJ1988]

Just thought, in regards to the pushrod, how does it do when you bleed the fronts? Does the pedal go down? Does the fluid come out at higher pressure then the rear?
Posted via Mobile Device

[airbrushguy]

Seems to come out well in the rear but even better in front. The pedal will not go down to the floor when you open the rear bleeders though.

[bollybib]

Originally Posted by airbrushguy

So what did you do, replace the valve? I have an extra one, should I just replace it?
Posted via Mobile Device

I left it alone. I have another one now that I'm trying to figure out if it's good or not.

[bollybib]

Originally Posted by Steve Hafner

. . . .

As far as the system not stopping well, I have the same problem with my new booster.

I asked this question a few months ago and got this answer:

. . . .

Here are a couple of pics from the 69 Overhaul Manual that might help. Good for single and double diaphragm Bendix units.

[Murphy IRE]

Again, my brakes slowed the truck to a stop. I checked the push rod clearence and as Longhorn Man said "That's not problem", but I did it anyway. I just installed the hydrailic booster and now the stop comes to a quick stop. LOL