Rear Brake Lines - No Fluid - 88 MJ

[YNGFrankenstein]

Hello All, 
I am in need of some guidance for the rear brake lines on my recently purchased 88 MJ. I replaced the rear brake shoes, springs, and cylinders because the rear brakes were disassembled and missing parts upon purchase. After finishing the rear brake assembly, I attempted to bleed the rear brakes using the 88 Comanche FSM procedure which includes opening a front bleeder to allow fluid to flow through the by-pass line.

Unfortunately, i've had no luck getting any fluid to come out of the rear brake bleeders. No fluid with front bleeders open or closed. I troubleshooted further by opening the brake line before it reaches the rear proportioning valve, but still no fluid.  

My next inclination is to disconnect the start of the rear brake line from the distribution block, disconnect the end of the rear lines, and attempt to remove any blockage. Any suggestions on the best way to achieve this or another path to for troubleshooting are more than welcome. 

Thank you, 

[Eagle]

If I remember correctly, the procedure for bleeding the rear brakes on the MJ calls for performing a complete normal bleed first, THEN opening a front bleeder to trip the shuttle valve and allow bleeding the bypass circuit. Did you do a regular bleed on all four wheels first?

 

[YNGFrankenstein]

Eagle,
Thank you for the reply. Yes, I attempted to do a regular bleed on all four wheels, but was unable to get any fluid to come out the right and left rear bleeder.
I tried adjusting the lever on the proportioning valve in all direction while attempting to bleed the rear brakes. I opened the lines going into and out of proportioning valve and found no blockage in the valve.  I also opened the 3 way brass fitting (meeting lines are - front of truck, - proportioning valve, - rear brakes) and was able to blow out the rear bleeders by pushing air through it. 

So I'm thinking there is blockage in the line coming from the distribution block or maybe there is something else i'm not taking into consideration. 

Thanks agin,  

[AZJeff]

It's possible that your flexible rubber brake line between the chassis and the rear axle has collapsed internally and is blocking fluid flow.   I would start by disconnecting the chassis end of that line and see if fluid flows.   If it does, then reconnect and check the axle end of the line in the same manner.

 

In all honesty, with vehicles as hold as ours, unless the flexible brake hoses are new or appear to be recent, replacing them is a wise safety precaution.

[YNGFrankenstein]

Ok. I was able to troubleshoot over the holiday weekend. I checked the flexible rubber line between the chassis and rear axel as AZJeff suggested. It was an aftermarket part installed by the previous owner and was still in good shape.

Next I opened the line coming out of the Master Cylinder's rear brake reservoir and couldn't get any fluid to come out. Then opened both ends of the brake line going from the distribution block to the rear brakes and that was also clogged. I was able to eventually unclog that line by pushing air through both ends.

Since the Master Cylinder was pretty grimy, and rebuilt ones are fairly inexpensive I replaced the Master Cylinder. After that, I ran some brake cleaner through the rear lines. Then I bled the brakes using the FSM procedure and it seems like i'm good to go. Other non-related issues are keeping the truck from running but that's a project for another weekend. 

Thanks to Eagle and AZJeff for the help. 

[Pete M]