Hello, all. I installed a complete Powerstop brake caliper/brake pad/rotor kit on my LJ on all four corners and also changed the emergency brake shoes and pins/springs. I have the original brake hoses (ordered new SS hoses but haven't arrived yet) and the original brake hard lines (as far as I am aware). I am having an issue bleeding the rear brake calipers. I barely have any flow at both calipers and only get a trickle when i pump the brakes. I used both a bleeder tool at the calipers themselves and the bleeder tool that pressurizes the system at the fluid reservoir. The front calipers are bleeding excellently and the brake pedal is firm despite the rear calipers not building pressure. 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.
2006 LJ Rear Disc Brake Bleeding Issue
- Thread starter hcoll003
- Start date
Just replaced the old rotors and calipers/pads. My LJ has rear disc brakes, no drums. Apparently they (rear brakes) were dragging before, which now makes sense
No, is it needed for the 2006 LJ?
Negative. Bleeder screws are all up. Also I cracked the banjo bolt on both rear calipers and pumped the brakes and a small trickle comes out. Flow is essentially comprised as to both rear calipers while flow is pretty good up front.
Sometimes you can reset the proportioning valve once you have everything back together again with a hard stomp on the brakes.
-Mac
-Mac
Per the brake wizard.
“We have noticed over many years of bleeding brakes on the TJ that it is very common to have the shuttle valve shift during bleeding. This is noticed during a bleed with the key on and the parking brake off. The brake light on the dash will illuminate showing that the shuttle valve has shifted and needs to be centered again to allow balanced flow to both front and back fluid circuits. The lock-out tool when installed will hold the shuttle valve in place to keep the flow even.”
If this did not fix the issue I would blame the cheap quality parts that PowerStop produces. Probably got powder coating inside the calipers during the manufacturing process. But I would start with using that tool. Not sure it would fix it now as the value already shifted but it’s recommended you use this tool during the bleeding process.
Kind of interesting, I've got the tool but never looked into what was happening in the valve.
Mr. Blaine describes a recommended reset attempt in the instructions for the lock out:
I pulled up the description in the manual, and it makes sense why that should work. It says the valve should specifically work under a hard braking event and the shuttle moves to shut off the low pressure (presumably open brake line) side, and illuminate the Brake MIL.
At the risk of being immediately shamed as an idiot. From the description (and the test that follows), I'd guess if the hard braking the sealed system doesn't work, that one attempt to correct it would be to crack a bleeder screw in the front to get the shuttle to move forward.
Here's that test description:
Thank you all for participating in another episode of GATORB8 learns something new.
Why does the braking system have to be so difficult on what is otherwise a very simple vehicle??? I have no brake warning lights illuminated on the dash. Any other thoughts of what the issue can be?
That is your clue that they aren't going to bleed correctly. The most likely culprit is the flex hose clipped to the rear upper control arm that feeds the rear calipers. Rust has probably happened inside the clip and is squeezing the hose and causing it to act like a check valve and also restrict fluid flow when bleeding.
The system is about as basic and simple as it can get. What isn't quite so simple is a clear understanding of all the problems that can happen that are not the fault of the system design.
KennethS
TJ Expert
It's not really difficult; it is actually a very simple system. The shuttle valve is a basic safety element used in nearly all vehicles to prevent complete loss of braking ability in the event of a hydraulic failure.
If you don't have the replacement on hand, heads up from my recent experience, hold the clip side with a wrench when you loosen the hardline. Mine had seized on and broke the clip before it loosened.
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?
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Ha, yup, doesn't seem like the hose would do much in that case.
Thanks for sharing about the system.
My BMB lockout is currently installed and ready to go. Picking up new MC to Valve lines on the way home so I can swap to the bench bled MC you recommended (old fittings are seized on).
I ordered that brake hose as well. Now it just needs to arrive. Blaine, I also installed the rear caliper pads with the "U" on the bottom caliper bracket. Do not remember if you said (in another unrelated post) the anti-rattle clip is what determines the brake pad position for the rear.
Doesn't matter much for the rear since a lot of pads only have the U on the end of one pad. Regardless of how we do it, what happens when you apply the brakes going the other direction?
To help future readers who may find this. Even if they were all upside down, the only consequence would be the inability to get the air out of them and resolve the spongy brake problem. No matter which way they are mounted, the path from the flex hose out the bleed screw remains the same and intact with no discernible effect on fluid flow.
To clarify, the tool is merely a convenience and never a necessity. What is required is a functioning brake warning light circuit and bleeding with the key on for a manual bleed so you know when to reset the shuttle and turn the light off. I grew weary of being annoyed at having to reset the light at every pedal pump so I went looking for the tool for two reasons, to buy and use one, then to put a link to it on the website so others could also get one. After purchasing many of them to find one that fit, I was unable to get one with the proper thread and stem diameter. So, I had them made. To date I have given away more of them than we have sold which is likely a reaction to how annoyed I still am over not being able to find one already done and the fact that something changed in the system that makes it a useful piece.
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