Ford Mustang Forum banner

1 - 20 of 26 Posts

·
Registered
Joined
·
62 Posts
Discussion Starter #1
I've looked over hundreds of forums and threads and from constant stress of finding the right answer so I decided to finally join a forum website and hopefully find the answer to my problems.

So here's the deal, I have a 1969 mustang with drums all around. I was driving to work one morning a few weeks ago and i went to stop and my brake pedal went all the way to the floor and didn't stop. I had perfect brakes up until then it's like someone cut the lines but I didn't have any leaks anywhere. I changed the master cylinder twice and bench bled both times, replaced all wheel cylinders and hoses, bled, bled, bled, and bled some more using all different methods (gravity, vacuum, one man, two man, etc.) and still the brake pedal goes to the floor. I'm on the verge of going completely insane.

Should i replace the pressure differential warning valve that regulates the fluid to the front and rear? Replace the master cylinder again? I'm out of ideas.

Any help is sincerely appreciated, thank you.
 
S

·
Guest
Joined
·
0 Posts
Welcome to AFM! Let me move this to the Classic Tech section for you and we'll get you figured out. Thanks for joining...

:bigthumbsup
 

·
Registered
Joined
·
1,127 Posts
Are you losing fluid that you cannot find a puddle? Did you get a pedal after pumping the brakes a few times? Did you get air while bleeding? My initial guess is that you are sucking in air some where. The most likely spot is the master cylinder reservoir cover seal. Please reply with a little more info so we can help. Good luck!
 

·
Registered
Joined
·
503 Posts
I know this is a dumb thing to ask but... is the master cylinder pushrod attached to the pedal arm? And if it is attached, is it fully engaging the MC?

And i'm guessing you dont have a brake booster??
 

·
Registered
Joined
·
4,555 Posts
If you have no leaks, then here are some possibilties, the master cylinder is bad, the pushrod is coming off the brake pedal, or the length of the push rod is wrong, some replacement pushrods are not the correct length, I always compare the original pushrod that was working to the replacement, before I replace it. Also check the steel brake lines under the vehicle and the ones from the distribution block to the wheels. Do you have power brakes? Good Luck.
 

·
Registered
Joined
·
1,275 Posts
I'm in agreement with other posters on this thread; if it was working fine, and now just goes all the way to the floor, it sounds like the push-rod has come out of the back of the master cylinder! Crawl under the dash and see if you can tell if the rod is on the brake pedal still.
 

·
Registered
Joined
·
1,153 Posts
If you have power brakes its the booster. I had the same issue with my 70' coupe. after two new master cylinders and countless hours of bleeding the brakes I got a tip to check the booster.
not knowing how to check it i took at $120 gamble and wa-la the brakes work like new now.
 

·
Registered
Joined
·
62 Posts
Discussion Starter #8
I thought it could be the MC so I replaced it in the first place, bled it and it did the exact same thing. Guessing I bought a bad master cylinder from where I work (Advance Auto), I went ahead and replaced it a second time, and still the same problem I don't have a power brake booster and I don't see any puddles on the ground in my garage. Also i felt around under the dash and the pin is still holding the pushrod on the pedal and its still attached to the MC. I pretty much checked every inch of all the brake lines and there is no wet spots so I'm guessing there is no leaks. I was also wondering, if the rear hose collapsed inside could that cause a low pedal? Also I found a broken hose from the transfer case but I'm guessing that has nothing to do with the brakes but I'm planning on replacing that anyways just in case.

By the way I never expected to have so many answers this quick, this forum site is amazing and I plan on using it for all my problems everyone has been very helpful and i really appreciate it.
 

·
Registered
Joined
·
593 Posts
When you had a friend help you bleed the brakes---When he stepped on the brakes and you opened the bleed valve at the wheel, did fluid come out?
 

·
Registered
Joined
·
74 Posts
I'm in agreement with other posters on this thread; if it was working fine, and now just goes all the way to the floor, it sounds like the push-rod has come out of the back of the master cylinder! Crawl under the dash and see if you can tell if the rod is on the brake pedal still.
+1 on this. If you verify all is good here, that only leaves the MC as you were thinking before.
 

·
Registered
Joined
·
62 Posts
Discussion Starter #11
Yeah, everytime she pressed the brake I opened the bleeder valve and in the rear i had a steady stream of fluid and no air, in the front for the longest time all I got was air but it slowly found its way out.
 

·
Registered
Joined
·
1,153 Posts
are your brake shoes on correctly, the front and rear (for each individual wheel) are different, there is a long shoe and a short shoe. short shoe goes toward the rear if i remember correctly.
 

·
Registered
Joined
·
236 Posts
Are the brakes adjusted correctly? They should be adjusted so there is minimal drum to brake shoe contact while spinning the wheel. They should be adjusted to the same level for all four wheels. Also, did you replace the rear brake hose?
 

·
Registered
Joined
·
62 Posts
Discussion Starter #16
I made sure I put the shoes on correctly by taking pictures before and doing one wheel at a time so I'd have the other to look at. As for the brake hose in the rear, I have not replaced that yet and I'm not sure if the adjusters are set correctly. I'm still scratching my head trying to figure out what else it could be. Next week I guess ill be replacing the rear brake hose and seeing if that helps (hopefully) :?:
 

·
Registered
Joined
·
465 Posts
brake shoes

:bigthumbsup
are your brake shoes on correctly, the front and rear (for each individual wheel) are different, there is a long shoe and a short shoe. short shoe goes toward the rear if i remember correctly.
aiways a good way to remember,B B,big shoe in back
 

·
Registered
Joined
·
38 Posts
first we need to address some common inaccuracies. a low brake pedal cannot be caused by a bad proportioning valve, a bad booster, the short and long shoes in the wrong position or a loose seal on the reservoir seal. pretty much the only things that will cause a low or no brake pedal is an external leak at a wheel cylinder, flex hose, steel line, a leak at the master cylinder rear seal an internal leak in the master cylinder or severely out of adjustment brake shoes. the hydraulic brake system is a completely sealed system that as you already know, can have no air in the system at all. any place that is drawing in air would also be leaking fluid. brake fluid is a liquid, and liquids cannot be compressed which is why it works. although the fluid flows through several components, it is basically a solid link to the brake shoes/pads. the proportioning valve simply sends a certain amount of fluid to the left and right front brakes and to both rear brakes. later model cars have a line for each of the 4 wheels, of course we're talking about pre ABS cars. even if the proportioning valve did have and internal leak/bypass, it would simply apply more or less fluid to either front or rear brakes. it's other purpose is to provide some kind of brakes in the case of a massive leak in the system rather than losing all brakes together. the reservoir cap seal could leak fluid around the cap, but as long as there is fluid in both chambers of the M/C, it will not draw air into the system. the brake booster simply assist in the pedal effort, there is no fluid in it and it is a solid link from the pedal to the M/C it will not cause a low or no pedal but will cause a hard pedal. a internally collapsed flex hose, front or rear will also cause a hard pedal but will not cause no pedal. Short or long shoes in the wrong position will not cause a no pedal situation. If fact, most brake shoe manufacturers do not even provide short and long shoes anymore. if you do happen to have short and long shoes, the short shoe goes toward the front.

back to your original problem. since you said that you had a sudden no pedal situation we can assume that the brakes are close to correct adjustment. if you don't have a mechanical failure such as a broken spring, which you would know because it would be noisy and you would have fluid pouring out of the drum/s and you don't see any external leaks, my first guess is that you had/have a bad master cylinder. assuming that you properly bench bled the M/C and properly bled the M/C at the lines when you installed it, you either have another bad cylinder, or still have air in the system. when bleeding the brakes, you should not pump the pedal more than 3 times and hold it down until you close the bleeder. the pedal should be pumped slowly. when the pedal is pumped rapidly or hard, it will airiate the fluid and cause no pedal. in this case, you need to let the car sit for a fairly long time in order for the bubbles to dissipate, you cannot bleed out these tiny bubbles manually. i;m willing to bet that you still have air in the system and patience is going to be the only way to correct the problem.
 

·
Registered
Joined
·
62 Posts
Discussion Starter #19
Would gravity bleeding get all of the air out of the lines? And I'm not sure if i am properly bleeding the MC but I've done it many different ways and looked online as to how its done. I'm literally pulling what's left of my hair out thinking about it. but ill go over it and do another check to see what i might have missed. Thanks again for the help, ill take as much help as i can possibly get.
 

·
Registered
Joined
·
93 Posts
Would gravity bleeding get all of the air out of the lines? And I'm not sure if i am properly bleeding the MC but I've done it many different ways and looked online as to how its done. I'm literally pulling what's left of my hair out thinking about it. but ill go over it and do another check to see what i might have missed. Thanks again for the help, ill take as much help as i can possibly get.
Ive been there, as well as most of us I suspect, and one rig I never got a solid feel to it. One thing to consider is that the system is highly sensitive to air in the lines, and patience will help. In you case its hard to say for sure what is causing the problem, and I suspect its still an air thing. On one rig I was having my daughter help bleed brakes, and she was inadvertently letting off the brake peddle ever so slightly and it took me forever to figure that out.

Also, dont rule out bad M/C, there were several I had to take back because they would not produce a solid feel. They were all rebuilt, so the last one I bought was brand new, and that one worked exceptionally well. Of course it sounds like you have an extreme case to which I cannot say Ive had. All my problems in this area were a too soft of a breaking feel, or one extreme was braking happening all the way at the floor. That was an unnerving drive. :)

My opinion, gravity bleeding is only for replacing the fluid in a working system, and even at that there is no guarantee. I prefer the two person method, or a pressurizing tool, but Ive heard that those are hard on seals.

another trick that may help is to take a bit of hose and put it over the bleed valve at the wheel cylinder and the other end into a clean pan of fluid. Then bleed normally, and this way if the peddle is released slightly before the valve is closed it wont suck air but suck fluid. ( that just seemed a bit odd to say. :) )

Edit: I re-read your OP, and realize Im suggesting the same thing you've covered. Im also thinking Mike Rojas is on to something. An immediate loss suggests a common point of failure like the M/C, or push rod kind of thing; I have lost an entire tire and drum once and I did not completely loose braking.

How about checking each wheel, taking the drum off one at a time, and having someone CAREFULLY press the brake and watch the action? (dont push all the way down, just enough to see that it starts to work.) That will tell you if the system is actuating or not and give you assurance that all the parts are there and working right.

I think you are at the point where you have to look over the entire system very carefully and meticulously to verify that every part is working the way it needs to, and work on a process of elimination.


Maybe you can describe what youve done to bleed the M/C... Ive tried it in the car, while attached to the system and it DID NOT work. I had to do it on the bench, or in the car works, but you have to take the output of the M/C and back feed into the reservoir, pump it until all bubbles are gone.
Good luck
 
1 - 20 of 26 Posts
Top