My brakes were working fine, but the fluid was dirty so I decided to flush the lines out and put fresh fluid througout. I flushed the lines then I bled them (farthest from the master cyl 1st). I also re-centered the pressure differential valve. Now when I start the car I can usually pump the brakes up and get them nice and firm, but when I put it in gear and go, the brakes now go to the floor and don't work. If I release the pedal and press again they will grab and then if I do it again it may go to the floor or grab or work OK if I pump them. There are no visible leaks and the master cyl stays full. I have re-bled them 2 more times very carefully and there is no difference. If I drive the car and pump the brakes they usually work. I have done this procedure many times on other vehicles with power brakes and never had any trouble. My 72 Mav 302 has original front/rear drums and the original master cyl. It sounds like the master cyl has gone bad, but this seems odd that it would just happen to fail after flushing the lines. Is there something different about Maverick manual brakes that I am missing and is not found in Maverick or Mustang books? Any help would be appreciated.
probaly all the dirt that was in the fluid was holding everything together in the master cylinder. Dont you just hate it when you try and do some preventive maintenance and it ends up biting you in the ass!
I agree with the others it's most likely your Master Cylinder. though I would not rule out any of the wheel cylinders. I recently redid my braking system including a new Master Cylinder they aren't that expensive and they're relativley simple to install just make sure you have a good flex head ratchet cause those bolts holding it on can be a pain to get to.
I had the same problem with a simple fix. Make sure your rear brakes are adjusted. They should be adjusted out until they drag on the rear drum. That was my problem after doing a brake job. Dan
Sounds like the same problem I've got, except I started having to pump the brakes BEFORE I started working on them. Glad to hear that ended up fixing it. I've got a 77 with power brakes. I thought at first I just needed to bleed them, but the bleeders on the calipers would not budge, so I ended up just replacing the calipers since they were cheap, and replaced the rear wheel cylinders because they were leaking. I've bled the brakes thoroughly using speed bleeders I installed so I could bleed them myself, and it is still exactly the same. The pedal goes to the floor unless I pump it first. Since I've replaced everything else, I guess the master cylinder is the only thing left that would cause no pressure in the brakes, since the lines are clearly open as I get plenty of fluid out when I bleed them. I just wanted to run all that by you guys to make sure it sounded right.
bad master cylinder make sure you bleed the master cylinder b4 installing it, and re bleed you entire system after install.
I've heard of that, but had forgotten about it. How do you bench bleed the m/s? I take it then that you install it full of fluid?
When you buy a new master cyl they come with instructions on how to bleed one (at least it should). You want to bleed it till no more bubble come out the hoses that are supplied.
Well, master cylinder didn't fix it either. Problem turned out to be that right-rear brake being way out of adjustment because of the self-adjust lever being missing. The problem did start gradually I guess, just didn't notice it until I started having to pump the brakes. Once I put a new lever in and screwed the star nut out most all the way so the pads were contacting the drum, the pedal firmed right up. Haven't had brakes this good in a very long time.
