This has only happened a few times but it kinda sucks. So a while back i was out wheeling. I was coming down off some steep rocks in 4 low. My brake pedal kept getting spongy until finally it hit the floor and left me basically without brakes. Not cool. So I had the brakes inspected and determined the rears where worn so I replaced the pads. Went out after the brake job and same thing happened. Spongy pedal that eventually hits the floor and leaves me rolling down stuff that I'd rather not just freely roll down. Pumping the brakes seems to add a little more resistance to the pedal but that of course leads to an uncontrolled decent. I've actually had to start using that stupid hill decent assist button, it helps a lot but I'd much rather be in control of the brakes instead of a computer. Has anyone else had this issue? Any suggestions on how to fix it?
I've got a 3" lift with 35's if that matters.
Thanks

 

Sounds like brake fade. How fresh is the brake fluid?

 

It's what came from the factory. It's a 2012.

 

If you are not losing fluid, it is most likely as the pads wore, you did not top off your fluid and you had enough of an angle to allow th master cylinder to not have the feed line covered with fluid and pumped just enough air into the master cylinder to cause the fade. Once again, my vote is lack of proper routine inspection and maintenance which falls on you, the owner.

 

Fluid level is full.

 

Can you can replicate it while applying the same pressure when in park or stopped? Using the same amount of pressure and time frame as when it happens on the decent. If there are no visible leaks or air in the system I would say the piston in the master cylinder is blowing fluid passed causing the pedal to go to the floor. Just a guess.

 

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you topped of periodically?

 

I'm betting on air in the system. I am also a believer in replacing fluid every two years. I would recommend new fluid and a system bleed.

 

It definitely sounds like air in the system, full master cylinder or not, there could be air inside the brake system. I would have it bled and see how that works.

Also, I don't believe that any JK has a Hill Descent Assist button? I'd be interested in seeing this.