4jeepchick4

alrighty, let's start at the beginning of this whole saga.
for awhile, my brakes would make a hissing noise when i pressed the pedal, just a vacuum leak but otherwise were in pretty good working order. this had been going on since i got the jeep i think, about two or three years ago. never really thought it was a major problem because it still stopped. just this past saturday, my dad replaced the vacuum booster so that it would stop venting. well now, my front brakes work fine and lock up but my rears don't do squat. so far here are all the fixes we've done:
new vacuum booster
new master cylinder
new rear shoes and drums
bled the entire system (on more than one occasion)
none of these have really seemed to help the problem we have now. the pedal, which used to have at least some resistance when pushed at first, now travels about an inch or two before you actually feel the brakes working. if i can, i'll try to get a video of what i'm talking about. it's like i press the pedal and it doesn't start to brake until it's about halfway to the floor. the problem as of now is that the front wheels lock but not the rear. when my dad looked at the drums, he said that the manufacturer cross hatch was still present which means the rears aren't doing all that they could, if they're even functioning. any ideas as to what's going on?

winston427

Do you have ABS?

4jeepchick4

i'm pretty sure it does

winston427

ABS is a little more difficult to bleed properly. There may still be air in the lines.

4jeepchick4

alright, first i could have sworn my dad told me that it had abs but it doesn't. my bad!

sean882

Make sure you start at the far back corner when you bleed.

If you jack up the back, of the car, put it on jack stands, and then start it up and put it in drive, can you stop the wheels from spinning with the brake? How about with the e-brake? **Make sure you are in 2WD** You don't need the back end way up in the air, just enough to let both tires spin.

Assuming you bled the brakes properly, the 'ease' of pushing the pedal down could just be the stronger vacuum helping move the pedal more. Mine has this same range of motion.

As for the back brakes not doing anything, (again, assuming they were bled), it sounds like they weren't adjusted properly. Easiest way to do this:

1.) Pull the drum off.
1a.) Look at the self adjuster. Is the latch making good contact with the star screw? Is the cable routed correctly around that 90 degree bend thingy? (Its a pain to get it seated properly - and use a little grease under it when you put it on). Replace any worn components you find here, as they do go bad over time.
2.) Rotate the star adjusting screw so the shoes come out more.
3.) Do this (trial and error) until the drum will still go on, but is rather tight. You should feel a descent amount of drag, and hear the two surfaces slipping, when you rotate the drum by hand.
4.) Repeat for the other side.
5.) Make sure the back brakes are dragging a bit before you put the wheels back on.
6.) Put the wheels back on, tighten everything up, and let the self adjuster work:
7.) Back up, come to a complete stop. Do this 7 or 8 times. The self adjuster on drum brakes will only adjust them when stopping from going backwards. So, make sure you back up and come to a full stop every once in a while.

The back brakes in the XJ are weaker, just by the way they are set up. Here is a writeup about how to even the front and the rear's stopping power. Be ware: On slippery surfaces, you will be much more likely to fishtail while braking if you have stronger rear brakes.

4jeepchick4

we replaced the proportioning valve and it seems to have worked. i think i'm getting rear discs for christmas now haha