1993 Jeep Wrangler cannot get rear brakes to apply (4WD - n

Tiny
JIMMOLINARO
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  • 1993 JEEP WRANGLER
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 76,000 MILES
I changed the front calipers and pads because they were severely burnt from an obvious seizing problem.
I also found partially restricted brake hoses on both sides which I assumed caused the burnt calipers & pads (discs not releasing all the way). So I changed both hoses. Then after an entire system bleed and a road test, the rear shoes refuse to activate and the vehicle lurches foward slightly when the brakes are applied. You could just feel the weakness of the rear shoes not applying. It is obviously a strained & uneven stop using only the front discs. Out of desperation I proceeded to change the proportioning valve that sits directly below the master cylinder. No luck. Same thing.
What seemed like a simple caliper/brk hose job has turned into a nightmare. Any thoughts on this?
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Monday, June 23rd, 2008 AT 12:40 PM

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Tiny
BREWER
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I'm not in position to help a 100% right now because I'm away from where I have the right info that will help. When I get home I'll check back - but - first question since this is an old post - has the problem been corrected?
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Sunday, July 6th, 2008 AT 5:33 PM
Tiny
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Sunday, July 6th, 2008 AT 11:01 PM
Tiny
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There are a couple things you need to do in order to determine exactly what the cause of this brake problem is. First, you say the brakes are grabbing at the front, and this has you believe the rear brakes are not functioning.

First, we need to confirm the rear brakes are not functioning. This will require you to gather an assistant to help you.

Remember, when doing the following exercises, do so with extreme care and attention. Recommend the use of jack stands and proper safety procedures.

With the rear wheels off the ground, the foot pedal needs to be depressed while another person tries to turn the wheel. I would suggest you could just use the emergency brake in this case, however the emergency brake operates using a cable rather than hydraulic fluid. While you are at it, try both cases to verify if either method works.

Now, IF the rear brakes are working under E-brake but not under pedal brake, then we have a problem inside the system from pedal to rear brake shoe. The question now is where. Most often, the problem is a leaking wheel cylinder. You said you bled the brakes on all 4 wheels, when you did this, did you also remove the rear drum and check the shoes? At the same time, did you cylinders for leaks? A quick way to check a cylinder for leaks is to pop the rubber cap off the bottom of the cylinder where the shoes meets - don't pry it all the way off though, just enough to see if there is fluid there. It is okay if there is a little sweat, but if there is lots of fluid, then the cylinder needs to be either replaced or repaired. Replacing is cheaper. This would be my first guess to check - IF the rear brakes didn't work when the pedal was pushed.

IF the brakes DID work when you pushed the pedal, then the problem with the grabbing is NOT because the rear brakes are not working, but instead because of something else that is wrong with the system overall.

This can be due to a couple of issues. The first and most common is grease / oil on the brake pads. The brake linings needs to be clean, use some brake cleaner to do this, and avoid contact with fingers or any other oil based product. (Remember hand have natural oils in them - avoid use of bare hands, and use proper gloves when doing the service)

Bare in mind the oil on the linings could also be in the rear drums - so when you are back there - you should also be cleaning all of that up too. Oil can readily contaminate the linings in the rear from blown axle seals or from the leaking cylinders as previously discussed.

If the problem is NOT in those. Get back to me with the results of the previous and we'll get back to the drawing board with a few more possibilities. The above are the most common causes of your symptoms and my money is on the fact this will sort it out. It could also be that air has got back into the rear system from when the brakes were bled - if a valve wasn't properly tightened, or came loose?

Good luck and let me know if you need more assistance :D
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Monday, July 7th, 2008 AT 12:13 AM

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