I think I may be an idiot

89 cherokee with weak brakes.

I was sure it was the master cyl. I just changed it, flushed all the fluid out of the lines and tested it. it is now worse than when I started. I have new pads/shoes, parking brake cables, rear wheel cyls, new master, new DS caliper and fresh fluid. I dont have to stop from road speeds as this is an offroad only jeep but I do need the brakes to hold on a steep incline. As of now I have a soft pedal and it will not pump up. The only things left in the system are rotors/drums, distribution valve (no warning lights are on) a caliper, vacum booster (booster holds presure over night so it is not leaking), and lines.

I have done many brake systems in the past but with all that I know is new I am out of ideas on what could cause this. It is acting like a bad master or air in the system. I gravity bled everything then presure bled to be sure. No air is coming out of the system, just clean, clear fluid.

I either need help or explosives. thanks for either,
Kevin

Did you bench bleed the new MC? If not, you probably have some air in it.

yep, bench bled then gravity bled the entire system, then presure bled the system with a friends help at the brake pedal, thanks for the thought though. I will probably bleed the whole thing again tomorrow but I dont think I am going to find any air. I am betting I will go through all this again and find out that even though it looks the same they gave me the wrong MC or it was defective from factory, Oh it is new not reman by the way.

Did you manually adjust the rear brakes? Is your self adjuster operational?
Did you adjust the rear by driving in reverse and applying the brakes several times?

Those are the only things I could think of (unless your calipers are on upside down - ask me - no, don't ask me how I know that one):laugh3:

ParadiseXJ said:

Did you manually adjust the rear brakes? Is your self adjuster operational?
Did you adjust the rear by driving in reverse and applying the brakes several times?

Those are the only things I could think of (unless your calipers are on upside down - ask me - no, don't ask me how I know that one):laugh3:

Click to expand...

...Upside down calipers? How would that even work lol.

iwannadie said:

...Upside down calipers? How would that even work lol.

Click to expand...

That would happen if your swapped the drivers and passenger sides. They bolt right up, but you can't bleed all the air out since the bleeder ends up on the bottom.

ParadiseXJ said:

Did you manually adjust the rear brakes? Is your self adjuster operational?
Did you adjust the rear by driving in reverse and applying the brakes several times?

Those are the only things I could think of (unless your calipers are on upside down - ask me - no, don't ask me how I know that one):laugh3:

Click to expand...

rears are supposed to be adjusted by the e-brake, but mine never really worked correctly. best to do it manually

2X on the upside down calipers! It's hard to believe how often this happens.

only replaced the one caliper and put the new one on the same as the old came off. I know this means nothing because there was a problem to start with but it feels like the back is where most of the problem is. I have the rears manualy adjusted to about two clicks before they drag. The e brake is weak but it is tight enough to hold. It just needs to be adjusted again because of the new cables.

thanks for trying I had never heard of upside down calipers before but it is good to know it can happen. if all else fails I will run new line and replace the distribution valve with an adjustable from summit. if that does not work it has to be a defective master. would not be the first time the new part was worse than the old. I have that kind of luck.

New caliper could have been for the wrong side. The bleeder should be at the top.

I'll chime in. I am guessing you still don't have the rears adjusted right. Having done several thousand brake jobs, this is how i adjust mine and they always feel nice and solid and never have an issue.

I put two lug nuts on to hold the drum in the same position it will be in when the wheel is bolted on. Just sliding the drum on isn't enough. Then I adjust them until there is noticeable drag, you will know you have when with the wheel bolted on you can spin the wheel and it makes 3 or 4 revolutions and stops. Anything more than that and they are too loose. You would be surprised how something so simple as proper adjustment can cause the pedal to rise and get more solid.

Before wasting time with the lines and a new prop valve. have someone pumping the pedal and lightly smack the prop valve. Sometimes they adjust and get stuck and need a light smack.

I think I have it partially fixed. The brakes will hold in high range under acceleration. the pedal still feels soft but it may just be a matter of adjustment from here if not it is has to be a bad Dist valve and the solution to that is run the front direcet and get an aftermarket reduction valve for the rears.

It seems I had a cracked drum. I was hitting the brakes and the drum was expanding with the shoes. Leave it to me to have one of the most rare problems I know of. I have heard of this before but never seen one. It is only a hairline crack and it does not go all the way through but it must be just deep enough to disipate the presure.

thanks for the sugestions everyone.