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Discussion Starter #1
Hello. So for the last year or so, every time I park my 2012 JKUR in my driveway (pretty steep incline) when I go to leave regardless if I backed in or am reversing out, my brakes lock up. The pedal will not push down at all...it is hard as a rock. If I drive uphill the brakes loosen up, but once I go back down they lock up again. If I put it in neutral the brakes seem to work fine. This also happens out rock crawling. It is pretty dangerous.

I have taken it to three mechanics and the dealer. No one knows what is going on.

Do you think it is my ABS system acting up? There are no lights on or anything.

Would doing the ABS Mod help? http://www.wranglerforum.com/f274/abs-esp-bas-off-mod-with-pictures-87119.html
 

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Sounds like it might be Hill Start Assist (HSA) behaving as designed?
 

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Discussion Starter #4
I am not 100% sure on the operation of the hill assist, but I do know it happens in 4 low when hill assist is completely disabled as well as when I do the 'steering wheel dance' and completely disable it. It is pretty dangerous.
 

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Discussion Starter #5
Any ideas on how to check it? It functions normally at all times except in my driveway and rock crawling...two scenarios that are hard to recreate at a mechanic shop. Typically, I work on everything on my Jeep and have done a lot...this issue is driving me crazy.

Sounds like something binding up in the pedal
 

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Hill start assist has no effect on the pedal. I'm not to familiar with the jk yet but usually the brake pedal is hinged and has a rod the pushes into the master cylinder on the firewall. When the pedal is locked up I'd just visually inspect everything on or around that area. Maybe the master cylinder/brake booster is ready to die?
 

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Discussion Starter #7
Yeah, I have had it inspected by three mechanics now. All of them say everything is working as it should. Which is surprising because none of them have recommended replacing any parts -- I would think they would just want to start replacing parts to get some money ... either I found some really honest mechanics or no one knows what is going on.

Hill start assist has no effect on the pedal. I'm not to familiar with the jk yet but usually the brake pedal is hinged and has a rod the pushes into the master cylinder on the firewall. When the pedal is locked up I'd just visually inspect everything on or around that area. Maybe the master cylinder/brake booster is ready to die?
 

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Are you saying the pedal locks up and does not apply the brakes, or the brakes lock up stopping the vehicle and also locks the pedal?
 

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Discussion Starter #9
The brakes are locking up...the pedal applies the brakes, it just gets really hard and has no movement. My Jeep eventually stops but I just have no control. For example, I was on Strike Ravine trail in Moab. I was coming down a really steep rocky section. I stopped at the top to figure out my line down. I let off the brakes to start down. After a couple feet I applied the brakes as normal. Then the brakes locked up. Thank God I was in 4 low. I creeped down the rest of the rock pile. In my driveway, I will start rolling, apply the brakes and get a grinding type noise. It will stop but I am pushing the brake pedal as hard as I can. If I roll down in neutral there is no problem--the brakes are fine. It is only in Drive and Reverse. I know someone will say go down in Neutral...that works in my driveway but doesn't work rock crawling.

Are you saying the pedal locks up and does not apply the brakes, or the brakes lock up stopping the vehicle and also locks the pedal?
 

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It almost sounds as if the boost in the power brakes is working backwards, pushing back against the pedal instead of the brake lines.

Does it do it on level ground or only if on a grade. Does it do it if you are at higher RPM (4 Lo?) or only at low rpms?

If you have a steep grade near a dealer, try it on that grade and if it does it there, take the service manager for a ride. Better yet, let him drive it.

I worked with a lady who had a car with the auto temp feature. (It heats the air and then applies A/C to bring it to the dialed temp) The A/C would not come on and all she got was heat. The dealer messed around with it to no avail until she took the service manager for a ride with his window switch turned off. He was begging for mercy before they got back (August in SE Texas).
 

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I will throw my two cents in because tjis one sounds like a good on.
First, if flat ground braking is unaffected at all then the hydraulic brake portiin of your system ks good. That includes the booster and the pedal.
That leaves the other syetem on your Jeep which is the anti lock brake/roll stability/traction control/anti roll back components. All of theses are tied into your hydraulic brake system by means of a control module and wheel sensors and a high pressure accumulator.
I wont go into details because i do know exactly who is behind the system on your wrangler. I will suggest you surf the web to get an idea of how they all work on your wrangler.
Then i would locate the fuse/breakers that power the system and test your wrangler in a safe location.
Again the hydraulic system will still worl with this system.powered down. But there will not be any aspect of the before mentioned features working.

I hope this helps. I know i am being vague but when you reseach those systems you will see why.

Good luck.
 

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Discussion Starter #12
Thanks! Yeah, that is true. I have actually had the dealer park on a hill and the problem even replicated, but they couldn't figure it out. They were pretty scared ha. It is definitely a safety issue. They said at first i had my hill assist on and said I somehow activated the complex steering wheel dance, which I didn't. Then they said I broke a sensor. They replaced it, but that didn't do anything. I am about to go rent a jk and see if it does the same thing.

It does do it on level ground as well, but I only really know that when there is a hill right after or before it. E.g. in my old driveway it was flat to begin with for 10 feet, then it quickly dropped into a steep decline. The brakes would lock up as I was rolling towards the decline. It happens in 4 low in a really low rpm range (just when rock crawling I am only going like 5-10 mph at the max). The problem has never happened at high rpms like in normal driving. And it usually only happens after it has been sitting for a while. So I thought it was a vacuum issue, but it seems everything is working fine.

It almost sounds as if the boost in the power brakes is working backwards, pushing back against the pedal instead of the brake lines.

Does it do it on level ground or only if on a grade. Does it do it if you are at higher RPM (4 Lo?) or only at low rpms?

If you have a steep grade near a dealer, try it on that grade and if it does it there, take the service manager for a ride. Better yet, let him drive it.

I worked with a lady who had a car with the auto temp feature. (It heats the air and then applies A/C to bring it to the dialed temp) The A/C would not come on and all she got was heat. The dealer messed around with it to no avail until she took the service manager for a ride with his window switch turned off. He was begging for mercy before they got back (August in SE Texas).
 

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Discussion Starter #13
Thanks MrSteve. I definitely know what you mean. I have read for hours and hours on this issue. I am too the point where I think I am going to install a switch in my console and bypass all of those systems. I just wanted to see if anyone thought that would fix it before I went in and cut the purple/light blue striped wire and intall an abs on/off switch. The steering wheel dance code doesn't do anything. I will look into it some more.

I will throw my two cents in because tjis one sounds like a good on.
First, if flat ground braking is unaffected at all then the hydraulic brake portiin of your system ks good. That includes the booster and the pedal.
That leaves the other syetem on your Jeep which is the anti lock brake/roll stability/traction control/anti roll back components. All of theses are tied into your hydraulic brake system by means of a control module and wheel sensors and a high pressure accumulator.
I wont go into details because i do know exactly who is behind the system on your wrangler. I will suggest you surf the web to get an idea of how they all work on your wrangler.
Then i would locate the fuse/breakers that power the system and test your wrangler in a safe location.
Again the hydraulic system will still worl with this system.powered down. But there will not be any aspect of the before mentioned features working.

I hope this helps. I know i am being vague but when you reseach those systems you will see why.

Good luck.
 

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Discussion Starter #15
That is a good point. I will look into that. I am also considering just replacing every single part that has to do with the braking system entirely. But that would probably be pretty expensive ... worth it though so I don't wreck my Jeep. That would be a sad day.

I'd have your ESP module replaced. Would probably nip it for good

Sent from my Nexus 6P using Tapatalk
 

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If your brake pedal is "hard" and/or "firm" after sitting for a while, your system is losing it's vacuum - plain and simple. Though, "where" it is losing the vacuum, is not so simple to find.
 
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