Twisty Posted April 9, 2008 Share Posted April 9, 2008 I hate my brakes. They never really worked, and the pedal would ALWAYS go to the floor (except when you slam on them)...even after 3 bleedings! Today I swapped in an XJ prop valve, and a new master from a parts MJ to see if I could get them to work. We bled them and they are worse than EVER! It almost doesnt stop!! Any Idea what could be wrong with my brakes? The rear is completely new within the last year and a half, and the front calipers/pads I bought less than a year ago! I have a trail run in 2 days, and don't want to drive it with these brakes. :hateputers: :mad: :headpop: Link to comment Share on other sites More sharing options...
Mitch Posted April 9, 2008 Share Posted April 9, 2008 did you get a master from an XJ with ABS? EDIT, sorry Tim, I just learned how to read. We had a tough time with my brother-in-law's s-10 blazer, but once the master was bled (by a mechanic) the breaks worked awesome! I don't know really how to bleed a master, or if you CAN bleed an MJ's master because my bro in laws was ABS... which I guess is different. Link to comment Share on other sites More sharing options...
Twisty Posted April 9, 2008 Author Share Posted April 9, 2008 I know how to bench bleed...and I have done it to other masters. I didnt do it with the new one because it was already bled when I pulled it out of the parts MJ. I've tried THREE different masters in the MJ, and two sets of calipers! Same result every time. Link to comment Share on other sites More sharing options...
maddzz1 Posted April 9, 2008 Share Posted April 9, 2008 Are you bleeding the rear height valve correctly? Is the brake booster bad? Does the brake light come on? Link to comment Share on other sites More sharing options...
Twisty Posted April 9, 2008 Author Share Posted April 9, 2008 Are you bleeding the rear height valve correctly? Is the brake booster bad? Does the brake light come on? I bypassed the rear height valve. It goes from the prop valve to the rear flex line. I don't think the booster is bad because I still have power brakes...its not a hard pedal at all. And I have no brake light (I don't even know if that feature works anymore. Link to comment Share on other sites More sharing options...
Kenosha Warrior Posted April 9, 2008 Share Posted April 9, 2008 Start from the top. Buy a new master. Bench Bleed it, then bleed your brakes as per usual. My MJ did the same thing and Bendix Masters, from experience, will do that with age and being sat around. don't kid yourself when it comes to brakes. A new master will whip this into oblivion. Link to comment Share on other sites More sharing options...
mjeff87 Posted April 9, 2008 Share Posted April 9, 2008 This won't help you immediately, but down the road consider installing a later model XJ dual diapraghm booster. I put one in my MJ this past summer, and I can lock up the 33's on it now. Had to relocate the washer fluid resivoir and run new lines to relocate the prop valve, but other than that it was a fairly painless swap Check your pistons in the calipers....one of them might be hanging up a bit. Jeff Image Not Found Link to comment Share on other sites More sharing options...
HOrnbrod Posted April 9, 2008 Share Posted April 9, 2008 This won't help you immediately, but down the road consider installing a later model XJ dual diapraghm booster. I put one in my MJ this past summer, and I can lock up the 33's on it now. Had to relocate the washer fluid resivoir and run new lines to relocate the prop valve, but other than that it was a fairly painless swap. Check your pistons in the calipers....one of them might be hanging up a bit. Jeff X2. Since you have tried several masters, you can prolly rule that out. I've installed many used master cylinders and never had a problem. I think your booster is shot. The 95/96 booster/master is one of the best mods you can make; I'd do it now. Jeff, your master-to-prop valve brake lines look great, like original. Did you retain your load leveling valve and reuse the original combination valve (that's what I did), or use the XJ prop valve. Image Not Found Link to comment Share on other sites More sharing options...
Twisty Posted April 9, 2008 Author Share Posted April 9, 2008 Well I tried to gravity bleed it...and that didnt work. Then I tried to bleed it again...and it didnt work! I'm fed up with this, and think I will call a shop tomorrow morning. I have to get this fixed, and I don't have a lot of time to do it! :hateputers: I'm currently researching the Dual Diaphragm Booster swap. Looks spiffy! Link to comment Share on other sites More sharing options...
Wildman Posted April 10, 2008 Share Posted April 10, 2008 Gravity bleeding is not the best way to bleed the brakes. The best way is to 'power bleed' but who has the equipment :dunno: I aways have success with the tube from the bleeder into a bottle, end of the tube submerged in brake fluid, and loosen the bleeder, fully pump the peddle 5-6 times, close the bleeder, add fluid to the master, and do the next wheel. And you can do this your self ;) Link to comment Share on other sites More sharing options...
Twisty Posted April 10, 2008 Author Share Posted April 10, 2008 I aways have success with the tube from the bleeder into a bottle, end of the tube submerged in brake fluid, and loosen the bleeder, fully pump the peddle 5-6 times, close the bleeder, add fluid to the master, and do the next wheel. And you can do this your self ;) I've tried this over 10 times on the MJ, and it still won't work!! I have a line on a 00 WJ master/booster. We'll see how it goes from there. Link to comment Share on other sites More sharing options...
86FUBAR Posted April 10, 2008 Share Posted April 10, 2008 don't forget that there is also a hydroboost upgrade u can do http://www.vancopbs.com/ProductDetails. ... ductCode=6 Link to comment Share on other sites More sharing options...
Twisty Posted April 10, 2008 Author Share Posted April 10, 2008 don't forget that there is also a hydroboost upgrade u can do http://www.vancopbs.com/ProductDetails. ... ductCode=6 You know, I was looking at our C2500 the other day, and I realized that it has a hydroboost brake set up. $1000 is a little much now. Its definitely a cool idea though, and would really be a sweet setup! Link to comment Share on other sites More sharing options...
86FUBAR Posted April 10, 2008 Share Posted April 10, 2008 don't forget that there is also a hydroboost upgrade u can do http://www.vancopbs.com/ProductDetails. ... ductCode=6 You know, I was looking at our C2500 the other day, and I realized that it has a hydroboost brake set up. $1000 is a little much now. Its definitely a cool idea though, and would really be a sweet setup! now if u got the kit which is 500$ and just tweaked ur curent power steering pump which is outlined in the DIY section u could save u some money Link to comment Share on other sites More sharing options...
Twisty Posted April 12, 2008 Author Share Posted April 12, 2008 Well the shop diagnosed the problem as a bad brake booster. Swapped one in from a parts MJ, and all it well! Thanks for the help! :cheers: Link to comment Share on other sites More sharing options...
HOrnbrod Posted April 12, 2008 Share Posted April 12, 2008 You're welcome! :cheers: Glad you got it fixed; not glad you had to pay a shop. :cry: Link to comment Share on other sites More sharing options...
Twisty Posted May 4, 2008 Author Share Posted May 4, 2008 Well I got a WJ master/booster today. I'll swap it in the next nice weekend we have. Link to comment Share on other sites More sharing options...
Eagle Posted May 4, 2008 Share Posted May 4, 2008 Keep in mind that the WJ master is set up for 4-wheel disc brakes. You will most likely need some sort of proportioning valve for the rear. Since I don't trust the stock load/height sensing proportioning valve since mine blew out, and I also don't trust the XJ proportioning valve, I'd suggest a Wilwood adjustable proportioning valve from Summit Racing. Link to comment Share on other sites More sharing options...
Twisty Posted May 4, 2008 Author Share Posted May 4, 2008 Keep in mind that the WJ master is set up for 4-wheel disc brakes. You will most likely need some sort of proportioning valve for the rear. Since I don't trust the stock load/height sensing proportioning valve since mine blew out, and I also don't trust the XJ proportioning valve, I'd suggest a Wilwood adjustable proportioning valve from Summit Racing. Does the limit the ammount of fluid that the master can push to the rear? Thanks for the information Eagle!! Link to comment Share on other sites More sharing options...
SuperWade2 Posted May 4, 2008 Share Posted May 4, 2008 don't forget that there is also a hydroboost upgrade u can do http://www.vancopbs.com/ProductDetails. ... ductCode=6 Next big mod for my tj will be the vanco big brakes... Probably won't do the hydro unless I go BIG Link to comment Share on other sites More sharing options...
Eagle Posted May 4, 2008 Share Posted May 4, 2008 Does the limit the ammount of fluid that the master can push to the rear? Thanks for the information Eagle!! You mean does 4-wheel disc limit the fkuid to the rear? No way -- a disc brake caliper requires a lot MORE fluid than a wheel cyinder for drum brakes. Also, disc brakes are not "servo assisted." Servo assist has to do with the way drum brake shoes are arranged. When you apply the brakes, the shoes try to rotate until they bind up against the pin, then they stop the drum. The geometry is set up so that in the forward direction they tend to draw the shoes into the drum harder. This is why the parking brake is more effective when you park nose downhill (forward) than when you park with the nose uphill (backward). My understanding is that ZJ and WJ systems for 4-wheel discs do not have any proportioning valve. In fact, I don't think any vehicles with 4-wheel discs have proportioning. So your WJ conversion might provide more braking to the rear than you want (as difficult as that may be to imagine after driving around with substandard brakes for awhile). Drive carefully when you first get it installed, and be mindful that the rear wheels may tend to lock up prematurely. Try some panic stops in an empty corner of a big parking lot and see how the brakes behave before you take it on the highway and forget about it. Link to comment Share on other sites More sharing options...
HOrnbrod Posted May 4, 2008 Share Posted May 4, 2008 Does the limit the ammount of fluid that the master can push to the rear? Thanks for the information Eagle!! You mean does 4-wheel disc limit the fkuid to the rear? No way -- a disc brake caliper requires a lot MORE fluid than a wheel cyinder for drum brakes. Also, disc brakes are not "servo assisted." Servo assist has to do with the way drum brake shoes are arranged. When you apply the brakes, the shoes try to rotate until they bind up against the pin, then they stop the drum. The geometry is set up so that in the forward direction they tend to draw the shoes into the drum harder. This is why the parking brake is more effective when you park nose downhill (forward) than when you park with the nose uphill (backward). My understanding is that ZJ and WJ systems for 4-wheel discs do not have any proportioning valve. In fact, I don't think any vehicles with 4-wheel discs have proportioning. So your WJ conversion might provide more braking to the rear than you want (as difficult as that may be to imagine after driving around with substandard brakes for awhile). Drive carefully when you first get it installed, and be mindful that the rear wheels may tend to lock up prematurely. Try some panic stops in an empty corner of a big parking lot and see how the brakes behave before you take it on the highway and forget about it. Most pickup trucks still use the height sensing valve which is a proportioning valve of sorts since it biases the rear brakes more under load. But the new ones are a far superior design to the MJ valves. Since mine was still working well I retained it. But I do plan to replace it with one from a Toyota pickup one of these days....... Link to comment Share on other sites More sharing options...
Twisty Posted May 4, 2008 Author Share Posted May 4, 2008 I get it now! I'm still rather inexperienced with brakes. Thanks for the help Eagle, and Hornbrod! 8) Link to comment Share on other sites More sharing options...
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