I have a 72 Cutlass and a 68 Skylark that both have the same problem. The 72 has power disc, and the 68 is manual drum. Both have all new (except hard lines and the proportioning valve) parts - shoes, pads, wheel cylinders, master cylinders, and soft lines. When we try and bleed them we have a very soft pedal to about half way then it stops. Once you crack a bleeder it will give you full pedal travel. When you try and drive them, it's like there no resistance and no brakes (even the manual car). Both have master cylinders from autozone. Both master cylinders were bench bled, and we bled the system like the manual says. I have never had this problem before. I'm thinking it is the master cyl. What am I missing? Tim
Low pedal and fading pedal can be caused by not getting all the air out of the master cylinder. When you bench bleed the master cylinder You "MUST" submerge the plastic bleed lines in the reservoir and pump the snot out of the master cylinder until no more air is in the lines. If you didn't do this you will have awful brakes. :TU:
We bled the heck out of them before installing them, and then after they were installed using a bleeder kit. I've never had brakes do this before- mush then hard, but no stop. Crack the bleeder, and you have another 2-4"+ of pedal travel.Close the bleeder and allow the pedal to come back up; step on it again and - mush then hard. Thanks Tim
Did you submerge the bleeder lines in the reservoirs when you bled the master cylinder? If not air will be trapped inside.
Yep. I am at a loss. Either the master cylinders are bad (both from autozone), something is blocking the line (on both) or both proportioning valves are bad (on both).
readjust every wheel brake adjuster to a light drag then retest , if the adjustment is out it will be that way but i do vote the autozone master are both bad, seen that a few times already
I had the same problem on my 71 when I switched the front to disc brakes. My friend and I used a combination of Mighty vac & pump-bleed method & finally got all the air out. It sounds like air in the lines. My $16.00 Auto Zone master cylinder is still working fine. We thought it was the master also. Keep at it. Good luck.
We have already tried readjusting everything and still nothing. I would like to think that with all the various ways and times that we have tried to bleed these stupid cars, that by now, there couldn't possibly be any air in the system (but who knows?). I plan on trying a different master cylinder to see if that doesn't cure this problem. Thanks. Tim
Speaking of coincidences, I just put a new master cylinder on my wife's 77 Cutlass today, and had the same problem. I bench bled the master properly, then bled in sequence to get all the air bubbles out of the system. The pedal went down with minimal resistence about 3 inches, then got stiffer. I test drove the car down the street and back, and only the rear brakes were working. I pulled it back into the driveway, left the engine running, and turned the wheel to expose the brake caliper bleeder. My wife pumped the pedal and I bled the front calipers again. Also, I had her do an emergency stomp on the brake pedal, which forces trapped air bubbles out of the proportioning valve, and the brakes are awesome now. I'd say try stomping and holding the brake pedal a few times, and maybe the air bubbles are trapped in the proportioning valve. Also, a lot of people aren't aware of the brake bleeding sequence. You start with the wheel furthest away from the master cylinder, and work your way to the closest one. It does make a difference. I hope this helps. -Josh Oh, oh!! I almost forgot. If you have recently changed all of those parts that you mentioned, double-check that you tightened all of those fittings. I re-did the brake system in my wife's 65 El Camino, and drove it to work to test-drive it, and found that I only hand-tightened the long brake lines that run to the rear brakes. Once I tightened those connections, I was able to properly bleed the system, and the brakes have been great ever since.
We have done the brake adjusting trick while driving- emergency stop, in reverse to set the adjuster= nothing. And my manual says to start at the wheel closest to the master and work to the furthest away. We have tried it both ways several times furthest away, and closest to and still the same problem. Gravity bleed, vacuum bleeder, pump the brake up and crack it-hold pedal-tighten bleeder and release= crap brakes. Tim
On cars where the master cyl. is tilted toward the rear, sometimes air will become trapped at the far end of it. The section that goes to the rears is particularly suceptible to problems from trapped air, and the most important thing is to start with a master that is COMPLETELY air free, otherwise all you will do is pump air all around the system and waste brake fluid. Twice I had the exact problem you are describing happen to me on a Ford Taurus, and it wound up being a restricted rubber hose on one of the rear wheels. Have you checked your hoses and are you CERTAIN they are not restricted? Best way to test that at this point, is with the brakes bled as best you can, and the wheels off the ground, have someone lightly step on the pedal and see if the brakes are grabbing on all 4 wheels. :Smarty:
They both have new soft lines, and we have looked at all of the hard lines. While bleeding the system, we have not noticed one line putting out less fluid than the others. My brother and I were talking about it earlier, and wondered if maybe we just got into a bad batch of master cylinders?????
If you're getting a hard pedal that sinks when you open the bleeders, it is making pressure. Once I got a bad one for a Skylark I used to own a long time ago, and what happened was they put the cup seals on the pistons upside down. When I'd push the pedal, it would sink and stay down and it was almost impossible to bleed even with the pressure bleeder I was using. ou: Did you do the wheel test yet with someone in the car applying the brake pedal?
Nope, haven't been able to try that test yet as it is raining out. I'm not sure that it is building pressure though. When you pump it up to bleed it, it's like mush and it feels like you have it on the floor (no more pedal travel). Then, when you crack the bleeder, it goes to the floor. But it doesn't spray out like it's under pressure, just has an even stream come out.
There's definitely air in there. Don't feel bad, that has happened to me more times than I care to admit. On my first time, I wasted over a qt. of fluid before I confided in a friend who came over to help me. I was certain it was not air in the master, but it was. ou: Start over, remove the MC from the car, and bench bleed it VERY SLOWLY and keep doing it with the hose completely submerged. Let it sit for about 10minutes, (for any aerated fluid to settle) and do it once more before putting it in the car. SLOWLY, TOO FAST = AIR. Then once it's in the car, LET IT GRAVITY BLEED. This may take over a half hour. If there's an excessive amount of air in the lines, sometimes gravity bleeding won't work. Pumping the pedal at this time will only draw more air into the m/c. Here is where pressure bleeding or vaccum bleeding works best, especially on the rears. If you have to work the pedal, only push it down once, then open the bleeder, keep the pedal down, then close it, then slowly release the pedal. You may have to do this 10 or more times, especially on the rears. And ALWAYS begin with the right rear, and finish with the left front. Avoid pumping the pedal numerous times and then holding until your final bleed. The reason to start with the rears first is so that you avoid the remote chance of drawing in air from the rear side into the front while you're bleeding. The rear side holds more fluid, hence more air, than the front and the front is always easier to bleed b/c the lines are shorter. If this doesn't work, I suggest you take it in to a shop to be power bled. Good luck! :TU:
http://www.v8buick.com/showthread.php?t=76640&highlight=bleeding Go to the above link and start reading.. Pay attention to the part where I start typing about 1/3 of the way down.:bglasses: Let us know how it works out for you. regards
I had this problem when i converted from 4 wheel drum to front disc and all new lines and prop valve. bench bled and no air, bolted up everything and blead and bled and bled and gravity bled. Even mighty vaced at the end. pulled 23" of vacuum and had it held 23" of vacuum and did not draw fluid, tried pushing the button on the prop valve and it didn't help would still hold vacuum. tried pumping brake with vac didn't help (though would loose vacuum) Ended up having to take it in and getting it power bled. boy does it now have a rock hard pedal now though.
