Brakes!!!

Any help would be greatly appreciated. I’m having a major issue with my 2016 JK you. It started to become difficult to get it to stop over the past several months. At this point I cannot get the vehicle to stop short at all. It will slowly stop, but I must put all my weight on a break, and the pedal eventually goes to the floor.
I’ve had it to a mechanic, and it is now in the dealership for over a month. Parts that have been replaced all four calipers, all four hoses, new rotors, flush out system, and three master cylinders, including the most recent OEM one at the dealership. I am into this for over 3K at this point. If anybody has any thoughts of what would give a soft pedal besides these options above, please feel free to share. I can easily tell that this is a problem because once I turn the vehicle on, I can just press on the break and it will go down 2 inches and feel some resistance, but then keeping pressure on a pedal, It will slowly go down another 6 to 8 inches. It used to never do that. Thank you for your time !!
I can’t believe I’m seeking advice that I can pass on to the experts at the dealership at this point… I brought it to the expert, but they can’t seem to figure it out

 

Dealership Expert is an oxymoron in my opinion with few exceptions.

Dealerships don't want mechanics to spend a lot of time on a vehicle because they make much more money on quick turnaround.

I'd first get the Jeep back home and have someone stand outside with the hood up. If you or the person outside hears a swooshing sound like air escaping I'd say it's the Power Brake Booster.

I'd then look for an old school mechanic that has good ratings and tell them the story and what you've found.

 

Here is what NAPA is asking for the part.

https://www.napaonline.com/en/p/NBB5477213

 

What’s the chance that they have replaced it three times and all have been bad??

 

I believe the OP said the master cylinder was replaced 3x but he didn't mention the booster.

 

Thank you for the ideas. I replaced the master cylinder once on my own. Then it was replaced with a second brand new one from Advance auto by my local auto mechanic. And then it was replacing third time by the dealership with an OEM. I did see a YouTube of where somebody said that they went through two cylinders that did not work and the OEM one fix it. Unfortunately, this is not my case.
I’ve been thinking about the booster as well, but all the mechanics are telling me that since I have a hard pedal when the car is off, that my booster is good. It’s pretty pricey for that booster, so I would rather try and figure if it could be anything else before I do that as a last resort.

 

Oh my bad. That’s right

 

I believe the booster is woth checking. As I said, if you hear air escaping it's almost certainly the booster.

On another note, here is a good video on the proper way to do a brake job. It's not overkill, I had a 2010 Avenger that I had to follow all these steps.

https://www.youtube.com/watch?v=qsozrTXfHoc

 

Another thought is it's a vacuume line leak to the booster. Remember the booster is air driven so if it's not getting vacuum to build air or its leaking, it will cause this issue.
I'm dealing with very similar issues with my 69 Fury. It is the booster on my Fury.

 

that’s what I’ve been thinking as well. And it’s also part of the reason why I bought it to the dealership so that they have the proper tools to check for a vacuum leak and pressures through the brake lines and stuff that which is out of my realm… unfortunately I’m coming to the realization that I am capable of doing more research for this problem that they are able to do. Again, I brought it to the dealer so they wouldn’t just throw parts at it, but rather figure out the actual problem and fix it, which is not my experience so far. It’s really pricey.
I just had bicep surgery, so I can’t do this work at this point , so my next step is going to be to get it back from the dealership, order a new booster, and have my local guy put it in. at that point, basically everything has been replaced on the brake system except the abs module , the vacuum line, and the hard steel lines for them. I’m really keeping my fingers crossed that it turns out to be the booster…
we listened for any hissing near the booster a couple weeks ago, and there was none…
It’s ridiculous because the dealership service manager has straight faced come out to me, handed me the keys to the Jeep and saying… All fixed! both times I got in the Jeep in the parking lot and basically slammed on the brakes and it would not even be enough to have a cup of coffee spill off of a seat. The jeep does stop but nothing like “short stop”, as it should ( throwing the occupants forward and locking up the seatbelts)
Thank you again for all those and given their thoughts. I’ll be sure to keep my results updated over the next couple of weeks.

 

Good Afternoon Surfodd,

I am giving advice but it's only my opinion so I don't want you to spend more money then you need to. If you're not hearing a swoosh when you step on the break, I'm thinking vacuum line may be more likely. Do you mind telling us what city/state you live in. If this is beyond your normal mechanic, maybe someone on here can recommend a more experienced/qualified mechanic for you. I know my mechanic can find a vacuum leak, he did it for my on a 2002 Chrysler 300M I used to own. Basically it has to do with introducing smoke to the vacuum lines.

These two videos are VERY good. Worth the time to watch them.

https://youtu.be/_IIHgURXfLE

https://youtu.be/zMok2y05jNE

 

A leaking booster will not create the scenario you're describing. If boosters going bad made you lose your brakes there would be no boosters in cars. You can drive all day with a booster unhooked--it just creates a slow-to-respond pedal you need to put a little more thought into. Someone needs to keep checking. The symptoms you describe are those of a problem in your hydraulics, not your air-override booster. It sounds like someone failed to bench-bleed a new master cylinder completely. Sometimes it can be pretty hard to ever get anywhere with bleeding the wheels until that's done well.

 

Update-
New booster put in and no change! ughh…
Only thing left is Abs module-
Dealership said they checked it on the computer and all looks good. wondering if zi should replace it anyway? It’s the only part of the system left , except the metal lines that absolutely show no signs of corrosion or being kinked..
Thoughts??