Bad brakes Baaaad Brakes (i'm sure this topic gets old)

[JNErotten]

Ok, ever since I've had the old wag the brakes have been kinda funny. They were shot at first. There seemed to be a new master included in a box with the jeep when I bought it and the old one was crap. All the wheel cylinders were cuput too. I replaced all and it seems that there is very little pressure going to the front brakes. I have good foot pressure but the braking is faint, faint, faint, then BAM!!! The rear brakes lock up. You have to be VERY careful and you can come to a slow stop ok, but go down just a little too quick and it locks good. My question is:
A. Could my primary piston in my master cylinder be screewed and not pumping enough pressure and then the back brakes piston activating fine after the spring depresses to engage it?

OOOOOR

B: Is it my proportioning valve. I've looked and looked. There is no pin to pull out while bleeding on this valve. I was hoping to email Pork Chop to confirm this (By the way,awsome rig & beutiful family PC...Congrats)

Keep in mind, I have bled and bled with a vacuum bleeder and the front brakes just don't seem to have any balls. I hope someone can help me cuase I've gotten used to it, but got forbid my girlfriend ever has to drive it. That would be funny at first, then dangerous in the end.

Thanks,
J
PS I have also bench bled the master many times, there is no air in it.

[Galactic_Battle_Cruiser]

I had a similar problem with my '82 Cherokee.I replaced the mastercylinder thinking it was the problem, then the proportioning valve, flex lines etc..... It turns out that the rotors had worn to the point that when I pushed the pedal, It would sink half way then build pressure. The back brakes would engage before the front and lock up. I put a new set of rotors on and it'll stop on a dime now. Maybe check your rotor thickness..?
GBC

[andy d]

does your rig have front drums? pre-74? if the fronts arent adjusted right or there is excessive front bearing play? or are the brake hoses shot? these are things i would check especially the hoses. 25yr old hoses get weird as they disintegrate internally. when you bled the brakes you had flow to all 4 bleeders? if not maybe a line is crimped?

[JNErotten]

Oh, you lit a fire with that one!!! LOL I can't tell you how much I wish I had rotors. This year wag has all drums. My Chero that I adopted, fixed, and ador, has front disk and rocks. But alas, you are rite in thinking that the rotors might have become steal brake dust on the rims of life. I just wish I had A rotor to check. Thank you for your help, and have an awsome holiday!!!

J

[JNErotten]

I do have flow to all bleeders. I'm gonna check to see if I have any line flex tomorrow while someone pumps. Def not a one person job. That seems like a shot in the dark, but yup you are right. At that age, I'd have abnormal bulgeing parts too I'm sure. Hell, I have that now (girlfriend smiles). Thanks for the advice.

J

but it still rolls over everything in it's stock having self ;)

[J20 project]

Are there auto adjusters on the front. I think the back had'm right? J20

[JNErotten]

All four have auto adjusters. After adjusting them, I think the front drivers side one still works. For this year wag, thats not bad, Heh Heh. I did adjust all though, made a small diff but you can tell the front still is lazy. Thanks for you help.

J

[River Beast]

speakinf of auto adjusters..... I pulled mine out about 2 weeks ago.... FROZEN SOLID!!! :eek:

I put them in a vice, broke them loose (heated if necessary) and clean up on a wire wheel. I then coated with anti-seize compound.

Seems that last time I went "river running" I foregot to get in there and do my preventative maintenance...OOPS.... it's been since May since my last river run.... so she was locked up good for a while...

just a hint to those... like myself... that can overlook little things tha make a BIG difference.

[Jake_S]

RB, was that the reason for your brakes not operating properly?
Jake_S

[JNErotten]

Ok, asked a friend help me check for bulging. He started to run away. After I explained what I really meant, me didn't mind helping. Anyways, the lines are fine. Thinking I should go ahead and just get a new master. Or does anyone think I should look towards another problem like the prop valve?

[JNErotten]

I just checked, please try to follow this. My front resevoir goes to my back brakes. And vice versa. When I step on the peadal with the cover off the master it's VERY obvious that the back brakes are working first, (big spray) and then when getting to the floor the front brakes rear res has a little spray. Isn't this backwards? The fronts should go first right? This is getting confuseing. Do I have the wrong lines goeing to the master ie. should i swithch the front and back lines to the rear and front resevoirs, or is my master just shot and the springs just not working right?
Or is it the prop valve?

Thanks,
J

[Sgt. Dave]

No, that sounds about right. And that brake fluid spray should take care of any unsightly paint in the area :D
Since you don't know the pedigree of the master cyl., it could be that you have a disk brake master on a drum system.VERY bad, no residual pressure.Lets the shoes snap back, gives very low pedal. You would get most of the pressure to the rear, rear wheel lock-up and poor braking action the rest of the time. The fronts provide about 70% of your braking action.
Just something to consider....

[River Beast]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Jake_S:
RB, was that the reason for your brakes not operating properly?
Jake_S<HR></BLOCKQUOTE>

This is a partial reason.. I gained back alot of braking from what I had.... but I still have the hard pedal.... but has been relieved some... I have been working WAY too much to do anything except eat ans sleep.... I will be digging in this weekend. I will start a new thread for the brake issues AGAIN....with findings

[Sgt. Dave]

Just a thought, has anyone checked to see if theres a master cylinder with a larger bore that will fit? Maybe from a 3\4 ton J truck?
It would give you more line pressure with the same pedal pressure. Could really help for those running big tires.

[Stuka]

Dint read all the post...but if it is drums front and rear....this is what I did.

I had to adjust the fronts way up..thebacks needed to be adjusted up as well. When you have the tire off, your should be able to turn the drum with resistance..not freely and not super hard. but it should be firm. And with drums you need to get themm pretty much all even, or it will pull when braking. Because unlike with disc, where the fronts do most the stopping..with drums..they are even on all 4.

[JNErotten]

Ooooh, are you sure? Four wheel drums brake evenly? ****, that would make sence and explain alotof things. And that would explain why the proportional valve doen't have any of those pins your supposed to pull out and in a certain way while bleeding. But you know this for a fact? That sure would be nice to know.

Thanks,
J

[Stuka]

on my rig it is....because my porportioning valve doesnt reall porportion much...no adjustments.....send evenly to all wheels. my 65 mustang is the same way (4 wheell drums)

[jeepbob]

The 69 does not have a prop valve just a junction block. Check to make sure that the brake shoes are on corrctly because if the primary and secondary shoes are reversed then you can get grabby brakes. Late Wags with drum brakes had a prop valve and the master cylinder was the same p/n as the disk brake master. I checked into this when I put the 78 prop valve and master cyl along with the power booster on my 65 with drum brakes. And the darn thing still don't stop like a modern rig.