bw71mach1

What else do I need to check? I have changed the brake fluid and bled the brakes. I have adjusted the rear brake drums. The front disc brake pads seems to be in good shape. But the first push on the brake pedal is a little soft. The second push is better and the third is good and firm. Suggestions?
71' Mach 1, 351 Clev

rmodel65

bad master cylinder? how are the rubber lines are they dry rotted?

bw71mach1

the lines seem to be okay. One looks recently changed. Someone told me that if it was the master cylinder the pedal wouldn't become firm. Is that true?

Cogtx

A bad MC may firm up momentarily, then slowly the brake pedal descends with pressure on it. If it stays firm, you may try bleeding the brakes again or locate where air is coming into the system.

bw71mach1

The pedal doesn't go soft after holding it down. I will try bleeding the brakes again to see if I have more bubbles. Can air get in the bleeder screw? The seal a the master cylinder looks good. Where else should I be looking.

LCC

Try bleeding the lines again (throughly). But I have seen the master cylinder do the same thing...new out of the box. Replaced it and good to go.

Cogtx

Look on the back brakes with the drums. Remove the drums and see if you have any leaks around the brake wheel cylinders.No an uncommon problem. If they haven't been replaced recently, you might have leakage. We had to replace all of ours on my son's coupe with drums all around. Bleed the line several times....good luck!!!

colostang

My experience with this is limited but everytime my 65' got soft in the pedal it was because on the the wheel cylinders had a bad seal and air was getting in the system. Bleeding breaks is kinda tricky sometimes so I would do the very best job I could....then do it again to be sure. I had way more problems with the wheel cylinders than I did the master cylinder, so I would look to them first. As always I like to give a disclaimer to the validity of my suggestions, as I am certainly no mechanic.

kalli

Hi !

first of all: when you bleed, start with the longest brake line first. Bleed until you get fresh brake fluid. Then follow with the next shorter line.
second: make sure to bleed properly (see below)
third: check if it is a thight system. It might leak in the master and liquid will go either into drums, or powerbrake vacuum dish (whatever that's called in english .. the big U.F.O at the master Cylinder). For this sit down in driver's seat. make yourselves comfortable and press the brake with firm pressure (no need to have the engine running). Stay and sit there and try to hold this pressure. If the brake pedal gives way slowly (you'll be down to floor after 5 minutes or before) you have a leak. If it holds the pressure it seems to be thight.

If this all does not help, please see here the very good tips on CJ pony parts:
http://www.cjponyparts.com/TechPoorBrakes.asp

kalli

---- proper bleeding ----
what I've seen some people do is scary:
open the bleeder screw, have someone pushing and releasing the break pedal like a madman and as soon as clear liquid comes they close the screw. this is all wrong.
correct:
a) have someone push the pedal
b) open the bleeder screw and the pedal will go down all the way to floor. Let him tell you when this is the case. close the screw. Make sure he does NOT release the break until the screw is closed. Tell him it's closed.
c) release the break pedal and continue with step a) again until all bubbles and dirt liquid is gone. Make sure from time to time that break fluid holder (where you refill) is not running empty.
This is the only way to make sure it's done properly when you have to do it manually.
If you have a machine that will pump new liquid into the break fluid holder, you can just open the bleeder screw and wait till all rubbish is gone. Close. Go to next one.
There are special bleeder screws that will allow mad pumping on pedal as they have a valve and spring in them. But I'm sure you will know when you got such equiment.

fastbackford351

Change your rubber lines. If one has been changed and the other has not, then one went bad. When one goes bad, the other isn't far behind it. Cheap money and probably go a long way towards fixing your problem.