2006 LJ Rear Disc Brake Bleeding Issue

[mrblaine]

I used both a bleeder tool at the calipers themselves and the bleeder tool that pressurizes the system at the fluid reservoir.

Not that it will change much, but can you expound on those two tools a bit? Are you saying you used a pressure bleeder at the master and then a vacuum style at the bleeders?

The front calipers are bleeding excellently and the brake pedal is firm despite the rear calipers not building pressure.

The firm pedal is likely due to the rear flex hose being restricted.

What is wrong, is it the proportioning valve or the rear hoses, or something else? I also attempted bleeding the brakes with the iginition on but no dice (I had read something about the older TJs needing to be bled with the ignition on). Thanks for the help.

There is no requirement that the ignition be on that will affect how the system bleeds for non ABS systems. We only prefer to have it on with a manual bleed so we can watch for the brake light in the event that we have one with the shifting shuttle valve problem.

For ABS systems, the manual base bleed is done, then the DRB is used with the key on to cycle the ABS pump so it can purge itself and then the manual base bleed is done again.

 

[hcoll003]

I used a hand pump bleeder at the rear caliper bleeders at first but did not get sufficient flow. Then I switched to the vacuum pressure bottle bleeder at the brake fluid reservoir which did not change the fluid flow/pressure at the rear calipers. The front caliper bleeders have decent flow. Hoping the low flow issue is that rear hose and distribution block on the rear axle that is my issue. I will keep everyone updated. Thank you

 

[mrblaine]

I used a hand pump bleeder at the rear caliper bleeders at first but did not get sufficient flow. Then I switched to the vacuum pressure bottle bleeder at the brake fluid reservoir which did not change the fluid flow/pressure at the rear calipers. The front caliper bleeders have decent flow. Hoping the low flow issue is that rear hose and distribution block on the rear axle that is my issue. I will keep everyone updated. Thank you

All you have to do to test is peel the clamp off the flex hose and then test. Even the visual will show the hose squeezed in by the rust.

 

[mrblaine]

I'm weary of finding incorrect info in the FSM. The plunger in the switch moves sideways, not up. The Switch does not have internal contacts. It actually has a pair of pins that are in fact connected to each other. It is part of a series circuit that does nothing but connect a few points to ground. In the case of this switch, the plunger moves, makes contact with the two pins and completes the circuit to ground which is the combo block itself via the booster to firewall connection as the most viable path.

The switch plunger rides in a detent in the valve rod. Spring pressure controls how high the pressure differential needs to be in order to shift the valve. Oddly, we never needed the lock out tool bleeding the earlier TJ, but in about 04, they lessened the spring pressure or changed the detent depth so they shift a lot easier. The tool prevents you from having to reset the shuttle at every pedal push on a manual bleed. (more annoying than anything else since you see the light turn on and hear the click)

That test is a bit bogus. Read step 3. Does it tell you to do anything other than connect a hose to the bleeder?

I often point out that the two pins are common to each other. I suspect given the lack of "aha" moments I see, maybe this will help. I cut the side off of one so you can see what it looks like down inside at the base of the pins.

 

[hcoll003]

*Update:

Received the new SS brake hoses for all 4 calipers, the rear distribution block hose in SS, and the new rear axle brake line. Now I just need to install it all. Will keep everyone updated. @mrblaine, my master cylinder is leaking a bit, I think it is the seal between the brake booster, what brand of master cylinder do you recommend if I decide to buya new one. Also, should I purchase your tool if I decide to swap it out?

 

[hcoll003]

Hello everyone. Good news, it appears my rear brakes are now working properly. It appears I was driving for over a year without rear brakes, including several trips to the Florida Keys. I changed all the caliper hoses to stainless steel, including the rear distribution block hose, and I replaced the rear axle brake line which included stainless steel brake hoses. No more rubber hoses. Not sure if the distribution block hose or the rear axle line was causing the issue but the rear calipers bleed beautifully after swapping the parts. Thanks everyone for your assistance. Getting ready to create another thread for the endless questions/tasks I have to complete on my LJ.