Jacob Ochs Posted February 1, 2015 Share Posted February 1, 2015 A few months back I did the 8.8 swap with the disc brakes. Well I got that all hooked up and the brakes worked alright and the pedal was stiff like it is suppose to be. Well I was at a local JY the other day and spotted the brake master cylinder and booster from a 96 XJ in great condition and pulled it and hooked it up to my 86 MJ. Well after all the lines and what not were hooked up I bled the brakes and the pedal was firm....Until I started the vehicle and it goes to the floor. Odd thin is that the brakes work pretty good the pedal just does not feel right at all. So we re-bled it the proper way again RR RL FR FL. And still had the same problem. So we bled the master cylinder itself. Hooked it up still the same problem. I have verified that the Booster is in good condition and even tried adjusting the booster push rod... Still nothing. This is probably the most frustrated that I have been with my MJ. So I'm off to buy another gallon of Dot 3 20 miles from my house again tomorrow after church! I'm in a bit of a rush as now I'm being told I'm a back up recruit for Feb. 9th! Sort of silly of me to start this brake project so close to then but I couldn't help myself I pulled it and I know the guy and he gave it to me for 30$. I thought it would be a plug and play dealio! Well sorry for my rant hahah so any help is greatly appreciated! Thank you guys very much for all the help these past few moths! :) have a great day all! Link to comment Share on other sites More sharing options...
Eagle Posted February 1, 2015 Share Posted February 1, 2015 How did you verify that the "new" booster is good? The problem you're describing is the classic symptom of a bad booster. How much did you change out? Are you using the XJ front distribution block/proportioning valve or the original MJ distribution block? Does your truck still have the rear height sensing proportioning valve? If so, did you follow the factory procedure to get the rear bypass line bled? Link to comment Share on other sites More sharing options...
Jacob Ochs Posted February 1, 2015 Author Share Posted February 1, 2015 How did you verify that the "new" booster is good? The problem you're describing is the classic symptom of a bad booster. How much did you change out? Are you using the XJ front distribution block/proportioning valve or the original MJ distribution block? Does your truck still have the rear height sensing proportioning valve? If so, did you follow the factory procedure to get the rear bypass line bled? I kept the original distribution block and load sensing valve from the MJ. I did not bypass bleed it, I didn't know there was such a thing! And there were a few tests I did for the booster that i looked up online; not sure how accurate they are though! Link to comment Share on other sites More sharing options...
HOrnbrod Posted February 1, 2015 Share Posted February 1, 2015 I've never had to do this, but here is the procedure from the FSM: After bleeding the brake calipers and cylinders the rear brake by-pass line must also be bled.Open a front caliper bleed fitting and depress the brake pedal to the floor. This will shuttle the by-pass differential valve and allow fluid to flow through the by-pass line. The brake warning light on the instrument panel will illuminate when the ignition key is in the ON position. This signals the shuttling of the valve.Re-Bleed the rear brake cylinders with the front caliper bleed fitting open.After re-bleeding the rear brake cylinders the entire system must be bled again.Bleed the brake calipers and cylinders in the following sequence:1st -- Right rear2nd -- Left rear3rd -- Right front4th -- Left front Link to comment Share on other sites More sharing options...
Jacob Ochs Posted February 1, 2015 Author Share Posted February 1, 2015 I've never had to do this, but here is the procedure from the FSM: After bleeding the brake calipers and cylinders the rear brake by-pass line must also be bled. Open a front caliper bleed fitting and depress the brake pedal to the floor. This will shuttle the by-pass differential valve and allow fluid to flow through the by-pass line. The brake warning light on the instrument panel will illuminate when the ignition key is in the ON position. This signals the shuttling of the valve. Re-Bleed the rear brake cylinders with the front caliper bleed fitting open. After re-bleeding the rear brake cylinders the entire system must be bled again. Bleed the brake calipers and cylinders in the following sequence: 1st -- Right rear 2nd -- Left rear 3rd -- Right front 4th -- Left front Okay thank you sir! I'm actually in the process of bleeding now I have to wait for mt bleeding partner to wake up from his nap first... I Will let everyone know if this works! If not the only thing I can think of Is bad master?? Link to comment Share on other sites More sharing options...
Jacob Ochs Posted February 2, 2015 Author Share Posted February 2, 2015 I've never had to do this, but here is the procedure from the FSM: After bleeding the brake calipers and cylinders the rear brake by-pass line must also be bled. Open a front caliper bleed fitting and depress the brake pedal to the floor. This will shuttle the by-pass differential valve and allow fluid to flow through the by-pass line. The brake warning light on the instrument panel will illuminate when the ignition key is in the ON position. This signals the shuttling of the valve. Re-Bleed the rear brake cylinders with the front caliper bleed fitting open. After re-bleeding the rear brake cylinders the entire system must be bled again. Bleed the brake calipers and cylinders in the following sequence: 1st -- Right rear 2nd -- Left rear 3rd -- Right front 4th -- Left front So I bought a new master and bled all brakes... Problem still presists. I tried doing that procedure you told me but I don't understand it... If I bled the brakes with a front caliper bleeder valve open then it'll just suck air into the system! Link to comment Share on other sites More sharing options...
Eagle Posted February 2, 2015 Share Posted February 2, 2015 I've never had to do this, but here is the procedure from the FSM: After bleeding the brake calipers and cylinders the rear brake by-pass line must also be bled. Open a front caliper bleed fitting and depress the brake pedal to the floor. This will shuttle the by-pass differential valve and allow fluid to flow through the by-pass line. The brake warning light on the instrument panel will illuminate when the ignition key is in the ON position. This signals the shuttling of the valve. Re-Bleed the rear brake cylinders with the front caliper bleed fitting open. After re-bleeding the rear brake cylinders the entire system must be bled again. Bleed the brake calipers and cylinders in the following sequence: 1st -- Right rear 2nd -- Left rear 3rd -- Right front 4th -- Left front So I bought a new master and bled all brakes... Problem still presists. I tried doing that procedure you told me but I don't understand it... If I bled the brakes with a front caliper bleeder valve open then it'll just suck air into the system! Only into the front circuit. That's the point. The bypass circuit on the rear proportioning valve is there so that if the front brakes fail, the rears switch to full braking power. In order to make that work, there are two lines from the front distribution block to the rear. A conventional bleed only bleeds the primary line, not the bypass. So you simulate a front brake failure by opening a front bleeder. There's no guarantee that's your problem, but there is a prescribed way to bleed MJ brakes, and if you haven't properly bled the bypass circuit you haven't bled the system. If it works, you're good to go and you've learned something. If it doesn't work, all you've lost is a half hour and a partial can of brake fluid. IMHO that's better than throwing parts at it and finding out the new parts didn't solve the problem. Link to comment Share on other sites More sharing options...
Jacob Ochs Posted February 2, 2015 Author Share Posted February 2, 2015 I've never had to do this, but here is the procedure from the FSM: okay thank you now I will do that procedure I just wanted better understanding! After bleeding the brake calipers and cylinders the rear brake by-pass line must also be bled. Open a front caliper bleed fitting and depress the brake pedal to the floor. This will shuttle the by-pass differential valve and allow fluid to flow through the by-pass line. The brake warning light on the instrument panel will illuminate when the ignition key is in the ON position. This signals the shuttling of the valve. Re-Bleed the rear brake cylinders with the front caliper bleed fitting open. After re-bleeding the rear brake cylinders the entire system must be bled again. Bleed the brake calipers and cylinders in the following sequence: 1st -- Right rear 2nd -- Left rear 3rd -- Right front 4th -- Left front So I bought a new master and bled all brakes... Problem still presists. I tried doing that procedure you told me but I don't understand it... If I bled the brakes with a front caliper bleeder valve open then it'll just suck air into the system!Only into the front circuit. That's the point. The bypass circuit on the rear proportioning valve is there so that if the front brakes fail, the rears switch to full braking power. In order to make that work, there are two lines from the front distribution block to the rear. A conventional bleed only bleeds the primary line, not the bypass. So you simulate a front brake failure by opening a front bleeder. There's no guarantee that's your problem, but there is a prescribed way to bleed MJ brakes, and if you haven't properly bled the bypass circuit you haven't bled the system. If it works, you're good to go and you've learned something. If it doesn't work, all you've lost is a half hour and a partial can of brake fluid. IMHO that's better than throwing parts at it and finding out the new parts didn't solve the problem. Link to comment Share on other sites More sharing options...
Jacob Ochs Posted February 3, 2015 Author Share Posted February 3, 2015 I've never had to do this, but here is the procedure from the FSM: okay thank you now I will do that procedure I just wanted better understanding! After bleeding the brake calipers and cylinders the rear brake by-pass line must also be bled. Open a front caliper bleed fitting and depress the brake pedal to the floor. This will shuttle the by-pass differential valve and allow fluid to flow through the by-pass line. The brake warning light on the instrument panel will illuminate when the ignition key is in the ON position. This signals the shuttling of the valve. Re-Bleed the rear brake cylinders with the front caliper bleed fitting open. After re-bleeding the rear brake cylinders the entire system must be bled again. Bleed the brake calipers and cylinders in the following sequence: 1st -- Right rear 2nd -- Left rear 3rd -- Right front 4th -- Left front So I bought a new master and bled all brakes... Problem still presists. I tried doing that procedure you told me but I don't understand it... If I bled the brakes with a front caliper bleeder valve open then it'll just suck air into the system!Only into the front circuit. That's the point. The bypass circuit on the rear proportioning valve is there so that if the front brakes fail, the rears switch to full braking power. In order to make that work, there are two lines from the front distribution block to the rear. A conventional bleed only bleeds the primary line, not the bypass. So you simulate a front brake failure by opening a front bleeder. There's no guarantee that's your problem, but there is a prescribed way to bleed MJ brakes, and if you haven't properly bled the bypass circuit you haven't bled the system. If it works, you're good to go and you've learned something. If it doesn't work, all you've lost is a half hour and a partial can of brake fluid. IMHO that's better than throwing parts at it and finding out the new parts didn't solve the problem. okay so I did this bleeding process and its a lot better but not how it feels in my parents Cherokees with the same setup! Any suggestions? Link to comment Share on other sites More sharing options...
Jacob Ochs Posted February 3, 2015 Author Share Posted February 3, 2015 I've never had to do this, but here is the procedure from the FSM: After bleeding the brake calipers and cylinders the rear brake by-pass line must also be bled. Open a front caliper bleed fitting and depress the brake pedal to the floor. This will shuttle the by-pass differential valve and allow fluid to flow through the by-pass line. The brake warning light on the instrument panel will illuminate when the ignition key is in the ON position. This signals the shuttling of the valve. Re-Bleed the rear brake cylinders with the front caliper bleed fitting open. After re-bleeding the rear brake cylinders the entire system must be bled again. Bleed the brake calipers and cylinders in the following sequence: 1st -- Right rear 2nd -- Left rear 3rd -- Right front 4th -- Left front So I bought a new master and bled all brakes... Problem still presists. I tried doing that procedure you told me but I don't understand it... If I bled the brakes with a front caliper bleeder valve open then it'll just suck air into the system!Only into the front circuit. That's the point. The bypass circuit on the rear proportioning valve is there so that if the front brakes fail, the rears switch to full braking power. In order to make that work, there are two lines from the front distribution block to the rear. A conventional bleed only bleeds the primary line, not the bypass. So you simulate a front brake failure by opening a front bleeder. There's no guarantee that's your problem, but there is a prescribed way to bleed MJ brakes, and if you haven't properly bled the bypass circuit you haven't bled the system. If it works, you're good to go and you've learned something. If it doesn't work, all you've lost is a half hour and a partial can of brake fluid. IMHO that's better than throwing parts at it and finding out the new parts didn't solve the problem. Well I got it figured out after driving for about an hour something seemed to break loose and now the brakes work great! Here she is all mocked up I needed that bigger booster to stop the awesome power of my 2.8L ;) Link to comment Share on other sites More sharing options...
Dillithium Posted February 3, 2015 Share Posted February 3, 2015 Holy crap sir, those lines from the MC to the distribution block have been bent a few times! Did you do it by hand? They look like they may have collapsed, meaning it is restricting flow. Link to comment Share on other sites More sharing options...
Jeep Driver Posted February 3, 2015 Share Posted February 3, 2015 I won't say anything..........no........nothing......... Link to comment Share on other sites More sharing options...
Jacob Ochs Posted February 4, 2015 Author Share Posted February 4, 2015 Holy crap sir, those lines from the MC to the distribution block have been bent a few times! Did you do it by hand? They look like they may have collapsed, meaning it is restricting flow. hahah that is actually a really bad angle ill take better pics of the lines tomorrow morning! But they are not collapsed Link to comment Share on other sites More sharing options...
Jacob Ochs Posted February 4, 2015 Author Share Posted February 4, 2015 I won't say anything..........no........nothing......... very bad angle will take better pics tomorrow I laughed when I saw how bad the lines look in that picture Link to comment Share on other sites More sharing options...
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