Tried to read a bunch of post on the subject, working 70 hours a week, most talk about it but no fixes. 2011 JKU with 35's and going to pull a small RV. Waited till the brakes were worn out then replaced with Power stop z36. Did have a front cal that was locked up. Every thing went well till bleeding the breaks. So second round of bleeding soft then hard as a rock. So close lets bleed one more time and make good. Went to hell. Now pedal goes almost to the floor. Breaks do work but do not have the warm wet fuzzy feeling when trying to stop. Took to local 4x4 shop and 2 weeks later they were apologizing to me about not being able to fix. Were so cool but said after reading 150 to 200 post about the problem. So said to drive it and see if it gets better, live with it OR could go to old school brakes with out abs and live with the dash light on. He did the same thing with a Toyota after he put in 1 ton axles. Said same problem but just by passed the ABS. Been looking over the net, but so far every one talks about break pedal fade, but all the problems solving is not working, do not have pulsing in break lines, leaks, replaced master cylinder, abs check good in computer, etc. Everything is great but the pucker hole on the seat is getting smaller. So if any one Knows the problem solving on this one get rich and pass on the repair.

 

Sounds like it might be that it needs the ABS bleed sequence. Friend of mine had similar symptoms, which happened after the fluid drained out with the calipers removed. He had problems getting it fixed by a shop as well, but it was fine after I did the ABS bleed.

It requires a scanner tool that can initiate the sequence in the ABS pump/solenoids. I've used my OTC scanner for it, but AlfaOBD and probably some of the other OBD2 scanners have it as well (although I haven't tested these yet). The sequence runs the pump, operates the valves, and tells you which caliper to bleed at a certain time. The whole system gets bled in the process. Most people will have a tech with a good scanner do it, it's easy with the right tools.

 

Shop ran the scanner tool through a full bottle of brake fluid, ran jeep through a field of grass, worked the hell out of the brakes. And soft pedal

 

I'd take it somewhere else. Still sounds like air in the system, it takes patience and more brake fluid sometimes.

For a full bleed, the order is regular bleed, ABS bleed (using scanner), followed by another regular bleed. Did they do it that way?

Regarding the master cylinder, it has to be bench bled before installation. If not, air usually gets trapped inside. Was that done right?
Edit: The same problem happens if the reservoir runs low on brake fluid during bleeding...

 

Shop bleed brakes with scan tool multi full time and tested, they did they research online to find multilevel people with same problems and did not charge me for reasearch time. They test drove the jeep many times. There is a problem with going to aftermarket breaks and even going to longer break lines for lifts. I'm not the only one with this problem as it has happen to many.

 

I have the same PowerStop z36 brakes and extended length brake lines. This will be my second time opening the system to install all 4 brake lines. I have no fade at all. No soft pedal. Actually, I think I've got a firmer pedal than my girlfriend's stock 2016. I know for a fact that they've got more bite between the pad upgrade and going to a higher quality rotor.

Also, when I opened the brake system this go around, second time recall, it was because a brake line had ruptured. I had no option but to allow it to puke all of the fluid out while waiting for new lines to come in. So a higher than normal chance of getting massive amounts of air into the system.

My point being- replacing lines, pads, and even a caliper is not call for it to be "ok" to go with no ABS or live with a light on the dash. To echo Mr. T- have another shop look at it. The reality of your situation is that your system is no different than it was designed from the factory so why not take it to the dealer? You're a customer asking for brakes to be bled and they have the appropriate tools. Tire size, pad brand, and extended lines don't change any of that.

 

The story that shop is giving you is BS. They sound like nice people, but this is the old I can't figure it out so it must be an aftermarket part issue excuse. Karl hit the nail on the head, brake pads and hoses don't change the essential brake system design. And unlike most other replacement parts, they have to meet DOT standards.

There are posts in every car forum about spongy brakes. Not finding this problem in a Jeep forum would actually be the anomaly. And if there are more issues like this with Jeeps, it because lifts, big tires, and more weight mean more Jeep hydraulic brake systems are taken apart.

The most common hydraulic brake bleeding problem I've seen is simply air in the master cylinder. Either from not bench bleeding properly during replacement, or from letting air into the master cylinder with low brake fluid (typically during bleeding). It's often hard to get the air out of a master cylinder, and takes either a lot of fluid, or removing it and bench bleeding it. I've had brake reservoirs go low while bleeding, and the four-letter words start flying because of all the extra work to get it right.

 

The only other thing I can think of besides air trapped in the lines or ABS module is leaking seal at MC. I know you mentioned having replaced that. Did you replace it with a factory unit? I've had a brand new Crown unit fail after a couple drives (talk about aggravating!).

 

It can take several forced ABS bleeds to get all the air out of the system. Never let your res go dry when doing a brake line service or while bleeding.

 

One of these stories is etched in my brain... Not only did air get (forced) into the system, but about a quart of fluid squirted into the engine compartment and soaked me underneath. First time using a finicky 1970's vintage pressure bleeder, what a mess to clean up.