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rear brakes not working???


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I know this is an mj forum but a lot of mj owners also own xjs so here I go - I just spent the day working on my 88 xj with the d44 rear end and installed new rear wheel cyl., shoes, hardware and drums. I did this because I nothice that my brakes needed replacement so I decided to change it all. Before I changed all the brakes I noticed that my rear brakes were barely engaging, as a matter of fact if I raised the rear end with the wheels of the air I could easly spin the rear tires and could not lock them at all. Well after all the work and the installation of new parts I see no diference what so ever, and yes, the brakes are nice and adjusted and the wheels still spind with little to no resistance. I blead the brakes several times too...Any Ideas???

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Pull the drum, have an assistant push the pedal just a little, slowly and be ready to stop as soon as you see movement (you don't want to be pushing the brake pedal too far with no drum on the axle). If the shoes don't move you know you have to find where the blockage is. If they move, then I don't know other than maybe you've got the wrong parts, drum is too big, or something like that. Then again you say they're "nice and adjusted", but if that's the case the parts should be sized right, if the adjustment is truly done properly.

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Unlike the MJ, the XJ uses a front combination valve that provides the proportioning function. Inside that distribution block just under the master cylinder there is a spring-loaded plunger with an O-ring. That's the proportioning valve, and as best I can figure out the way it works is to NOT allow any brake fluid to the rear unless/until you really stomp on the brakes.

 

My '88 XJ also has no rear brakes. My game plan (as soon as I get a free afternoon) is going to be to remove that nut from the front of the combo valve, which will reveal the plunger and spring inside. (Remove carefully, that spring is STRONG!) I will then remove the spring, take the O-ring off the plunger and set the plunger fully into the cap plug, then reassemble and bleed the rear brakes.

 

That should give you better rear brakes than you ever thought an XJ could have.

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Eagle beat me to the punch, I've just included the link (with pictures) for rebuilding the valve.

 

 

If you adjust the rear "self-adjuster" so that there is a little drag on the wheel when you spin it, then the the rear drums are adjusted correctly.

 

You may have a common XJ problem with the proportioning valve.

 

Read thru this, and rebuilding your proportioning valve should solve your problem -

 

http://www.lunghd.com/Tech_Articles/Sus ... ve_Mod.htm

 

 

NOTE........This is for XJ's only, not to be done on the MJ's :no:

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Thanks guys for all the great answers, especially eagle and Wildman. Today I wanted to try removing the o-ring at the combination valve just like the article said. I read and re-read the article so I felt this modification will definitely help my rear brakes so I contacted my good friend CW for an additional helping hand. After work I stopped by his house and we had it all done in about 1hr!!! Including clean up, putting the tools away bleeding the brakes and a quick lap around the block to test my newly improve brakes. All I have to say is that it works better that advertised; I was able to lock my wheels on pavement with no problem. I will recommend this modification to anyone that is lacking breaking performance. Thanks CW for the helping hand and thanks you guys in the forum for nailing this one again

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Glad to hear everything worked out for the better :clapping:

 

Must be really nice to have CW in the hood to help out too :yes:

 

 

As JTDesign would say....... K.I.S.S.

 

It's always the little things that make a Big Difference........with out throwing a bunch of parts at it :D

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since this thread has been solved i'll add on to it,

 

my truck has had the rear prop valve bypassed and it ate a set of mopar shoes in <20k miles. doesn't that seem a bit excessive? (it was never driven with the e-brake on, lol)

 

most vehicles don't need rear brakes for 80-100K miles, is it the prop valve mod's that cause the rear brakes to wear so quickly?

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most vehicles don't need rear brakes for 80-100K miles, is it the prop valve mod's that cause the rear brakes to wear so quickly?

Nope. More likely either the shoes were set up too tight and dragged, or (perhaps more likely) the parking brake cable(s) are rusty and the parking brake doesn't release all the way.

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