Whats the problem? Brakes

trailjeepman

trailjeepman

Well-Known Member
Joined
Jun 7, 2005
Location
Raleigh, NC
OK.....I have had stopping issues for a while now. I have an 83 CJ7 with power brakes on 35's and geared 4:10. I has always seemed as if I just have manual brakes.

So this weekend I changed the master cylinder to one for a 84 Suburban with JD7 brakes. This is a bigger bore master cylinder and hoped to help with stopping power. Well it didn't. And before you ask, I did bench bleed it and have bled all the lines. I do have a very stiff pedal. I also changed the combination valve but that didnt help either. The brakes feel the same as they did before I began.

I also started thinking that maybe my booster is not working but I am not sure.

I read in the haynes manual how to check the booster by pumping the pedal a few times with the engine not running. Hold in the pedal and crank it. It says the pedal should give way toward the floor. Idid this and it did give way a little but not much.

My question is....Do you think its my booster? If not then what else could it be.

Thanks
Nathan
 
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thats the direction i was thinking. just because you have more "power" going to the brakes doesnt mean you have more breaking power. larger calipers/rotors and and more pistons is what you need. a larger booster is a step in the right direction but no where near the final solution.


for better grip you need bigger hands and bigger fore arms. bigger fore arms wont help any if you cant get your hand around the ball.
 
fwiw.....when i was running stock cj axles and breaks, i ran a yj booster and mc and had awesome breaks. Im pretty sure you are still runnin stock axles correct?
 
Yes stock axels. I dont think its the pads or calipers. It used to stop good a while back. There has gotta be something else. The pedal is just too stiff as if the booster isnt helping me any.
 
if your pedal is very hard and your breaking sucks, then that's a symptom of a bad Booster.

have you checked to make sure your calipers are froze up?
 
Lift front axle in the air, have someone spin the tire and then stomp the brake pedal. does it stop? does it stop abruptly? does it slow to a stop, does it keep spinning.

it should stop the wheel abruptly.
 
Ok checked the calipers and they seem alright. I took everything back apart and now I think my booster is ok.(hooked the vacume line up to it while it was in my hand and pushed the rod. I pushed right on through with ease.) Now I hooked everything back up in order starting at the pedal. I am getting plenty of movement through everything until I put the master cylinder back on. Now I am only getting about 1/2" to 3/4" of movement through the rod on the back of the booster. Does this sound right? I do know the master cylinder will push in further than that from when I was bench bleeding it. Probably 1 1/2" to 2". Also I drove it a little and when I am at a stop and release the pedal just enough for the brakes to start squeeking, I can hear both the front and rear grabbing so I think I am getting brake to all four wheels.

I am just concerned about the rod movement. Any suggestions?

Thanks
Nathan
 
I have now replaced the booster, master cylinder, prop valve, and both calipers. I still have a very stiff pedal and it still feels like I just have manual brakes.

Is there anything else that could cause this?

I know replacing the pads with a better quality will help with stopping but I am more concerned about the stiff pedal. I am only getting about an inch of push through the master cylinder piston. Is that normal?

What would happen if I just get rid of the prop valve and run directly off the master cylinder?

Thanks
Nathan
 
I am not sure I understand what you mean by hard pedal....
Is it a firm brake pedal or a dead stop cant push farther?

You need to make sure you have the right length pushrod for your brake pedal assembly and MC...there are a million ways these could not match and if they dont you would not get enough piston compression in the MC to build pressure in thee lines.

Also as said, check your flex lines, if they collapse inside you will get similar symptoms
 
Flex lines are braided stainless and yes I seem to have plenty of flow when bleeding the lines. The pedal is both firm and it seems to only push to a certain point and wont go in any further. I made the push rod. It is long enough to set the pedal in the all the way out position. If it is too long would I have this problem? I wouldnt think that the lenghth of that rod would matter that much other than the brake light switch.
 
I've heard folks say you can "over extend" the MC when bench bleeding... supposedly damages the cups.

A push rod that's too long generally holds pressure on the brakes and you figure it out when they start smoking/lockup! :lol:
 
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