So I put a new posi rear under my 70 skylark. I replaced the rear axle brake lines, wheel cylinders and brakes. was all set to spend about and hour last Sunday bleeding them and hopefully take her out for a spin..... So I spent about three hours trying to bleed them, ran a GALLON of brake fluid thru the rear reservoir of the master cylinder, I used a vacuum bleeder at the rear cylinders, gravity bled, pumped the brakes, scratch head, repeat, bang head off wall, repeat,. Finally I gave up. I could not get the air out of the rear brake lines, I could not get any type of solid pedal. Now I have done brake work all my life, I do know how to bleed brakes, I have never had trouble like this. I had one leak at a fitting which I got to seal up. no other leaks seen. I have the rear of the car jacked up, could that be screwing me up? I mean I got it to gravity bleed so???? I read somewhere that if you push your brake pedal full stroke, all the way to the floor, there is a chance you can mess up the seals in the master cylinder because the piston never travels this far under normal operation. I did fully stroke the brake pedal so could I have messed up the piston seals? I did notice that if I pushed the brake pedal with the lid removed from the master cylinder, it would shoot oil from the rear oil reservoir and hit the hood, I don't remember ever seeing this happen before? Im getting ready to order a master cylinder for lack of any other ideas, anyone ever have a similar experience?
The experience of thinking I was losing my mind when trying to figure something out on my car? Yes, Ive experienced that quite a few times. Its not fun Its a possibility the master didn't survive the bleeding process. Do you have a low pedal, a soft pedal or just nothing at all? Is the brake light on the whole time or does it just go on when the pedal hits the floor? Do you get pressure out of the bleeder screw when you crack them open? If you inadvertently step on the pedal with the cover off the master, yes, the master will do its impression of old faithful, so thats normal.
brake lights only on when I press the pedal. no pedal at all. no pressure at the bleeders but I do have oil there.
Does the pedal pump up at all? If so , you can try bleeding the rear brakes at the master. Pump up the pedal as you would normall and then crack the line at the master and see of you have pressure there. If not, Id say your looking at a new master
When you had the leak at the fitting it's possible that when you released the brake pedal it sucked air into the lines. It is possible that the air that was sucked into the system made its way to the master cylinder . That plus the pedal going to the floor and perhaps tearing a seal in the master . A new master cylinder properly bench bleed and then a gravity bleed at all 4 wheels will cure it
Even if you have air in the line you USUALLY will feel something. The P valve (if you have front disc) could also have hung open ..it has a little button with a boot over it on the brass junction block...check that too. Other than that. do the master rebleed and be sure you have a good clear stream as someone presses the pedal down. BE sure NOT to hit the pedal again till the steel line is reinstalled and tdo not let the resivior empty or you will start ALL over again. After that I say let the rear cylinder on the passenger side gravity bleed...then the driver side gravity bleed. Now with the bleeders closed just let someone slowly push the brake pedal down and crack the bleeder at the same time they push and the person in the car needs to tell you the exact time they get to the floor so you can closet before the bottom of the travel. IT will be QUICK so explain to the person your having push. Do the other side the same way ... keep doing this till you get some kind of pedal...IF AGAIN it does not pedal up.... WELL you got trouble alright. I have had to do this sometimes and it seems to get me out of the jam of the system getting totally leaked out. Check the p valve junction block, rear proportioning valve That could be your headache too Hope that gives you something else to get it fixed. Good luck, Jim J D
I have front drum, there is a junction block down on the frame below the master, I didn't follow the lines to see what its purpose is. I think you guys are probably right, I somehow got air trapped at the master cylinder. at this point I think I am going to replace it to eliminate the possibility that I tore the piston seals. thanks for everyone's help so far, I was starting to think that I was loosing my mind.
If it is drum all the way around then it does not matter. Wow...you in a tough spot. HAve you tried to crack open the front just to move the system along and freshen up the fluid in the front.
Here's how I solved my issue, but I think we were/are in similar spots. http://www.v8buick.com/index.php?th...-pedal-straight-to-floor.330870/#post-2776554 Keep us posted, a lot of good solutions have already been shared.
I did Jim, sat for probably two months open but like I said I ran almost A Gallon of brake fluid thru the rear reservoir and out the rear bleeders so I cant imagine that there is any air between the master cylinder and the rear cylinders?
If you haven't bench bled the master, you will never get pedal. Mine sat open for two weeks, filled it and bled it. Pedal went straight to the floor every time. Removed the master, rebled it, and once installed I immediately had pedal back in the car. EDIT: The piston will be pushing air within the master, and that air will slowly compress the fluid, but barely. That air within the cylinder itself is likely the problem. Your lines are probably fully bled, but bench bleed the master and slap it back in, and I bet you'll have pedal of some sort before a final bleed.
cool, that must be my issue then, no need to remove to bleed tho, correct? no reason I cant do it on the car, same thing, use brake pedal to stroke the cylinder rather than a screwdriver.
Are the steel brake lines original, or at least older? If so, there may be a chemical coating accumulated in them that holds air bubbles similar to soda or beer bubbles clinging to the side of a glass. I had a case many years ago where I could not achieve satisfactory brake pedal height and brake performance after a simple caliper overhaul. I used a couple gallons of fluid, tried a pressure bleeder, gravity bleeding, used a helper, etc. I tried replacing nearly the entire brake system, some components more than once to no avail. Master cylinder, front and rear hoses, front and rear calipers, rotors, even the vacuum booster. The steel lines were all original and in the end, I discovered that the air bubbles in the lines clung to the inside walls of the lines and would not travel to the bleeder screws. What fixed that particular car was tapping on the lines from front to rear while bleeding them at the same time. It was amazing to watch bubbles and foam appear at the bleeder screws with each tap on the lines! When this procedure was finished, the brakes worked perfect. I realize this is a crazy idea, but I had invested around 40 hours in this car trying everything else. It worked for me, maybe, theres an outside chance it will work for you if nothing else does. Good luck!
Had something similar happen on my GS and a friends Nova after we converted to front discs. Seems we had air trapped in the splitter/delay valve. What worked on my car then later on his after he had bled a gallon of fluid was this. Instead of gently pushing the pedal when a rear bleeder is open STAB the pedal then close the bleeder. Do this a few times then bleed gently. NEVER pump the brakes against closed bleeders like uncle bubba. Otherwise I would be suspect of the master cylinders condition.
