Bad Brake fade while going down obstacles

[1is2many]

Has anyone else experienced this?

3.5 inch lift with 37’s other than that pretty much stock JTRD.

On the street pretty much normal breaking even going downhill but for some reason when I’m going off road downhill or down and obstacle the brakes almost go to the floor and get mushy and fade bad. I’m wondering if it could be the antilock braking system acting up I think next time I go off-road I’m gonna pull the fuse for the antilock brakes and see if that makes a difference.
I was in Sedona on Saturday and going down devils staircase. I had almost no brakes, luckily I have the diesel and had it in 4low and kept it in manual 1st gear. I threw it in neutral so the engine wasn’t pulling down the obstacle and it helped but wasn’t a good feeling. This isn’t the first time it’s happened.

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[Jefe1018]

Hmm I’ve not had that issue, every really. Time to get that warranty to work for you!

 

[Rusty PW]

Bleed the brake system and go to brake pads with more bit. Something like EBC Yellowstuff pads.

 

[mx5red]

If your car stops coming off the highway, then it doesn’t seem like brake fade. Wouldn’t it have the same issue then?

 

[Rusty PW]

If your car stops coming off the highway, then it doesn’t seem like brake fade. Wouldn’t it have the same issue then?

He's not the only one to report this problem.

 

[dcmdon]

I don't know what it is, but I can guarantee you its not brake fade.

That kind of low speed crawling heats up the brakes only a tiny fraction of what one stop from 70 mph on the street will do. (Remember that kinetic energy, which is what the brakes turn into heat, increases as a SQUARE function of speed. So stopping from 70 mph puts FORTY NINE times as much heat into the brakes as stopping from 10 mph.)

Brake fade is a very specific problem caused by the brake's inability to shed the heat that you are putting into it. The pedal may go to the floor and it may get mushy, but it's not brake fade.

If it was, you would have much more of a problem on the road.

That leaves a few things.
1) ABS problem.
2) Master cylinder problem
3) air in the brakes

 

[Lunentucker]

Is BLD playing a role in this?
I really don't understand enough about that system to venture into that answer, but I'm here to learn.

 

[JeepOfTheseus]

Mushy sounds like air in the system. I installed Teraflex “BBK” and have been battling this ever since. The mushiness seemed to be directly correlated to how much air I still had in the lines, but I feel like I never got it completely flushed.

 

[yoda13]

Mike has done this a few times in the nearly two years I’ve owned it. On road, or off, it doesn’t matter to it’s occurring. It will also go months at a time not doing it.

 

[mx5red]

Is BLD playing a role in this?
I really don't understand enough about that system to venture into that answer, but I'm here to learn.

Maybe system got the brakes super hot and just noticed it going down devils staircase? Seems like that’d require a whole lot of BLD action non-stop..

 

[1is2many]

I don't know what it is, but I can guarantee you its not brake fade.

That kind of low speed crawling heats up the brakes only a tiny fraction of what one stop from 70 mph on the street will do. (Remember that kinetic energy, which is what the brakes turn into heat, increases as a SQUARE function of speed. So stopping from 70 mph puts FORTY NINE times as much heat into the brakes as stopping from 10 mph.)

Brake fade is a very specific problem caused by the brake's inability to shed the heat that you are putting into it. The pedal may go to the floor and it may get mushy, but it's not brake fade.

If it was, you would have much more of a problem on the road.

That leaves a few things.
1) ABS problem.
2) Master cylinder problem
3) air in the brakes

I understand you're being very specific with the word fade, however it's still brake fade (reduce in friction) the braking system fades away it doesn't have to be from heat but yes that's most common. Loss of stopping power, or fade, can be caused by friction fade, mechanical fade, or fluid fade. Pedal gets mushy and goes to the floor pumping doesn't help so it's not typical air in the line. Most likely not ABS or I would be getting an ABS light, I am leaning toward whatever powers the master cylinder is dropping power/voltage at idle.

I just had it do it today in a parking stall for the first time ever, I think at idle the system is not getting correct voltage/pressure somehow. It has never happened while RPM's are above idle, which explains why it would happen when I throw it in neutral coming down steep grades or obstacles. If it's not ran from a vacuum which others have mentioned that it's not... I am now researching the braking system from the master cylinder, where and how it's powered and fed from. Hopefully I can find a schematic online somewhere.

 

[1is2many]

Mushy sounds like air in the system. I installed Teraflex “BBK” and have been battling this ever since. The mushiness seemed to be directly correlated to how much air I still had in the lines, but I feel like I never got it completely flushed.

It's been bled, plus if it had air in the lines it would be mushy and would require pumping the pedal all the time, not randomly. There is an issue with the power feeding the master cylinder I'd almost bet money on it.

 

[Rusty PW]

It's been bled, plus if it had air in the lines it would be mushy and would require pumping the pedal all the time, not randomly. There is an issue with the power feeding the master cylinder I'd almost bet money on it.

If you try bleeding the brakes again. Take a small hammer and tap on the master cylinder and the ABS module. Sometimes air will get trapped there.

 

[mx5red]

I don’t know if it matters for this, but why do you put it in neutral to use the brakes?

 

[Rusty PW]

I don’t know if it matters for this, but why do you put it in neutral to use the brakes?

The Rubi diesel in 4Lo has enough torque at an idle to push through the brakes on the trail.

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