Master cylinder replacement and brake bleeding hasn't fixed a soft brake pedal

[Banshee]

Have you considered the rubber brake lines from the body to the brakes? The rubbing in those 'soft' lines can become more flexible with age & may be expanding under pressure. I replaced mine with braided steel lines some years ago, so would not get that extra stretch that even new rubber lines has. (2" lift & front disconnects, I needed longer flexible lines. Replacing the rubber hoses with braided steel teflon lines on my bike made a huge difference to the feel there as well.)

I would try having someone press the brake pedal hard while I had my hand around the line to see if I can feel any expansion, on each corner.

[RLT]

Just wonder about operation of ABS unit
When it gets activated naturally whilst driving, would this do the same action as a scan tool ?

[JayOh]

From what I understand you need to do a regular bleed after activating the abs, so taking it for a drive on a dirt road and hitting the brakes isn't going to clear any bubbles by itself. I've even seen some suggestions the regular bleed needs to be done immediately after the abs has been activated otherwise the air bubbles have the opportunity to return to the abs..

[RLT]

Originally Posted by JayOh

From what I understand you need to do a regular bleed after activating the abs, so taking it for a drive on a dirt road and hitting the brakes isn't going to clear any bubbles by itself. I've even seen some suggestions the regular bleed needs to be done immediately after the abs has been activated otherwise the air bubbles have the opportunity to return to the abs..

I've never done a bleed after activating ABS over 11 years of ownership, seems a bit excessive to me.
That apart, as time has now progressed, is there any update on your quest to achieve a more satisfactory brake operation ?

[JayOh]

I've been trying to get it booked into the local Jeep specialist since January, but he's been swamped. Called him again last week and he's still swamped but said to bring it up so he could take a quick look and test drive and maybe advise my local mechanic what to look at next..

Half an hour later he's checking it out in his driveway, making lots of hmmm noises, pumping the brakes, switching off the motor and pumping the brakes, hmmm noises now HMMMMMMMMMM noises.. he says the pedal should be firming up with the engine off, but he can still keep pumping.

We go for a drive and he's still saying hmmmm a lot while braking, then the reassuring statements - "mate, this is really bad" and "it's been years since I've had a problem like this.." I think he is genuinely puzzled, not trying to soften me up for a "this is going to cost a lot.." discussion.

We get back and he says we need to book it in so he can go over it properly. Finally! Could be brake lines swelling under pressure or the brake booster not allowing the master cylinder to close properly. Or something else..

So it's booked in for this Monday, hoping this will be the end of it. I may end up just going for a big brake upgrade if it's not an easy fix.

Sent from my SM-G998B using Tapatalk

[Fishframe]

Originally Posted by JayOh

I've been trying to get it booked into the local Jeep specialist since January, but he's been swamped. Called him again last week and he's still swamped but said to bring it up so he could take a quick look and test drive and maybe advise my local mechanic what to look at next..

Half an hour later he's checking it out in his driveway, making lots of hmmm noises, pumping the brakes, switching off the motor and pumping the brakes, hmmm noises now HMMMMMMMMMM noises.. he says the pedal should be firming up with the engine off, but he can still keep pumping.

We go for a drive and he's still saying hmmmm a lot while braking, then the reassuring statements - "mate, this is really bad" and "it's been years since I've had a problem like this.." I think he is genuinely puzzled, not trying to soften me up for a "this is going to cost a lot.." discussion.

We get back and he says we need to book it in so he can go over it properly. Finally! Could be brake lines swelling under pressure or the brake booster not allowing the master cylinder to close properly. Or something else..

So it's booked in for this Monday, hoping this will be the end of it. I may end up just going for a big brake upgrade if it's not an easy fix.

Sent from my SM-G998B using Tapatalk

In an earlier post someone mentioned swelling brake lines and they fixed their Jeep with a similar problem to yours by replacing to good quality stainless braided lines. Looks like they were correct.

[RLT]

Well it would be nice if that is all it was.
In the 11 years of ownership and 166,000 Km I've only changed out the brake hoses once when replacing the calliper's.
Rear callipers been done twice.
Maybe steel braided ones next time !