Another mushy WJ brake thread - JeepForum.com

 
LinkBack Thread Tools
post #1 of 12 Old 04-19-2009, 12:21 AM Thread Starter
Chandler
Registered User
 
Join Date: Sep 2005
Location: Chandler, Arizona
Posts: 195
Another mushy WJ brake thread

I hate to ask but since it's a potential safety issue I want to make sure I get as much info as possible. I did search all the old discussions.

I have a 2004 WJ and bought in 2005 used. The brakes have been mushy the whole time. I just thought that's how they were. Last summer I changed my front rotors and pads. The mushy brake feeling was worst than before. To the point I thought something was wrong.

Today I changed my rear rotors and pads and added speed bleeders. I bled the system the best I could and purged out the old fluid. The brakes feel firm with power off but as soon as I start the pedal goes to the floor. I still have great stopping power.

Today I was searching for info on adjusting my ebrake and noticed other threads about mushy brakes and now realize this isn't normal.

I haven't noticed any fluid loss or lack of stopping power. I want to diagnose the issue and resolve since my wife drives the WJ back and forth to work. Friday someone rearended her and I don't want that to be her next time.

I want to diagnose the master cylinder and figure out how to test each caliper. If possible any advice would be great.

If I change the master cylinder how do I make sure I don't create air in the ABS system?

How do you bench bleed a master cylinder?

Thanks in advance.


2004 WJ Overland
Chandler is offline  
Sponsored Links
Advertisement
 
post #2 of 12 Old 04-19-2009, 08:20 AM
micifus
Original GC'er
 
micifus's Avatar
1993 ZJ 
 
Join Date: May 2006
Location: Upstate, NY
Posts: 2,955
every chrysler vehicle I have driven I have noticed "mushy brakes" maybe yours is more so then normal. A lot of times I will double pump the brake pedal. Push it in a little let off then push in again, the second push the brakes should be a lot firmer. Maybe this is just nature of the beast.

1993 Jeep Grand Cherokee Limited 4.0L I6
- OME Springs - 30"x9.5" Yokohamma's A/T-S -RE Shocks - JKS Quicker Disconnects - FM70 - E-Fan Conversion - 249->242 Swap -

1970 Jeepster Commando 225 V6
32"x11.5" BFG A/T
4" Lift



"For every one thing I fix two things break"
micifus is offline  
post #3 of 12 Old 04-19-2009, 08:38 AM
ZeeJay1997
Registered User
1997 ZJ 
 
Join Date: Dec 2008
Posts: 8,612
My brake fluid was really nasty so i spent all day cleaning and bleeding new fluid through. 2 quarts of brake fluid later, the brakes were not as mushy.

The reservoir had gunk in it so I took it off and cleaned it. Now the fluid is bright and clear.

Unless it is pulling when brakes are applied, I wouldn't start chasing a single caliper.

http://autorepair.about.com/od/fixit...ench-bleed.htm

Google much?
ZeeJay1997 is offline  
post #4 of 12 Old 04-19-2009, 08:41 AM
baxy
Registered User
 
Join Date: Mar 2009
Location: cranbrook
Posts: 1,443
old brake fluid that has been opened and sitting on the shelf for a long time will make brakes feel mushy
baxy is offline  
post #5 of 12 Old 04-19-2009, 09:09 AM
rm2001wj
Registered User
 
rm2001wj's Avatar
2001 WJ 
 
Join Date: Aug 2005
Location: Memphis, TN
Posts: 3,229
I suspect that the pedal never goes to the floor while the WJ is rolling; but it does after you are stopped and if you push hard on the pedal. I believe that is normal and is due to the way ABS is designed on the WJ. When you are stopped, the wheels are not turning, but you are pressing hard on the brake pedal. The ABS thinks the wheels are locked (they are not turning) and tries to reduce the pressure on the brakes pads. The wheels still are turning so more pressure is reduced. The net effect is that the pedal goes down to the floor as the ABS bleeds off the pressure.

Bottom line is that the brakes act normally if you don't push hard on the pedal when your WJ is not rolling.
rm2001wj is offline  
post #6 of 12 Old 04-19-2009, 09:59 AM
indept
Registered User
2000 WJ 
 
Join Date: Aug 2007
Location: New Jersey
Posts: 1,322
Quote:
Originally Posted by rm2001wj View Post
I suspect that the pedal never goes to the floor while the WJ is rolling; but it does after you are stopped and if you push hard on the pedal. I believe that is normal and is due to the way ABS is designed on the WJ. When you are stopped, the wheels are not turning, but you are pressing hard on the brake pedal. The ABS thinks the wheels are locked (they are not turning) and tries to reduce the pressure on the brakes pads. The wheels still are turning so more pressure is reduced. The net effect is that the pedal goes down to the floor as the ABS bleeds off the pressure.

Bottom line is that the brakes act normally if you don't push hard on the pedal when your WJ is not rolling.
The ABS computer knows if your Jeep is moving. It won't activate when you're stopped.

Quote:
Originally Posted by micifus View Post
every chrysler vehicle I have driven I have noticed "mushy brakes" maybe yours is more so then normal. A lot of times I will double pump the brake pedal. Push it in a little let off then push in again, the second push the brakes should be a lot firmer. Maybe this is just nature of the beast.
That's an indication that you have air in the system & they need to be bled.

2000 WJ 4.0L 42RE 242 TC
190,091 miles & counting
indept is offline  
post #7 of 12 Old 04-19-2009, 10:30 AM
rm2001wj
Registered User
 
rm2001wj's Avatar
2001 WJ 
 
Join Date: Aug 2005
Location: Memphis, TN
Posts: 3,229
Quote:
Originally Posted by indept View Post
The ABS computer knows if your Jeep is moving. It won't activate when you're stopped.
...........
The only way that the ABS computer "knows" if the Jeep is moving is by getting signals from the wheel speed sensors. If wheels are not turning, there are no signals.

Nothing is wrong with the brakes if they behave as I described above.
rm2001wj is offline  
post #8 of 12 Old 04-19-2009, 11:56 AM
xJoshxx
Web Wheeler
 
xJoshxx's Avatar
2012 WK 
 
Join Date: Sep 2008
Location: Burlington, Kentucky
Posts: 5,533
Quote:
Originally Posted by baxy View Post
old brake fluid that has been opened and sitting on the shelf for a long time will make brakes feel mushy
Brake fluid Absorbs moisture in the air is the reason why.

Sold4" Hybrid lift TeraFlex coils IRO Adjustable LA's Jks tracbar 1.25spidertrax spacers 265/75/16 Dura-tracs
Quote:
Originally Posted by moPowered View Post
The SRt-8's are a liberty design.
2011 WK2 ORA2 sold
2012 WK2 SRT8 - Current
99 WJ Limited Lifted.
2001 WJ stock 4.0 304k miles
xJoshxx is offline  
post #9 of 12 Old 04-19-2009, 04:29 PM
indept
Registered User
2000 WJ 
 
Join Date: Aug 2007
Location: New Jersey
Posts: 1,322
Quote:
Originally Posted by rm2001wj View Post
The only way that the ABS computer "knows" if the Jeep is moving is by getting signals from the wheel speed sensors. If wheels are not turning, there are no signals.

Nothing is wrong with the brakes if they behave as I described above.
Doesn't the ABS computer monitor vehicle speed otherwise the ABS would be pulsing away when you're stopped at a light.

2000 WJ 4.0L 42RE 242 TC
190,091 miles & counting
indept is offline  
post #10 of 12 Old 04-19-2009, 05:25 PM Thread Starter
Chandler
Registered User
 
Join Date: Sep 2005
Location: Chandler, Arizona
Posts: 195
I guess I'll call it good for now. I would like to get a cap for the master cylinder though and do the trick someone mentioned to use a valve stem to pressurize the line and bleed them.

2004 WJ Overland
Chandler is offline  
post #11 of 12 Old 04-19-2009, 06:48 PM
rm2001wj
Registered User
 
rm2001wj's Avatar
2001 WJ 
 
Join Date: Aug 2005
Location: Memphis, TN
Posts: 3,229
Quote:
Originally Posted by indept View Post
Doesn't the ABS computer monitor vehicle speed otherwise the ABS would be pulsing away when you're stopped at a light.
WJs don't have a vehicle speed sensor. The PCM and ABS computer both use the wheel speed sensor signals. The pulsing is due to the ABS releasing pressure when a wheel stops turning and then applying it again when the wheel starts turning again. Of course, it only does this in response to heavy brake pedal pressure. Light pedal pressure, like that normally applied when the Jeep is stationary, doesn't trigger any particular ABS response.

As I mentioned earlier, it is heavy pedal pressure when not moving that lets the pedal go down near the floor. Pulsing would only occur if the wheels starts to turn as the ABS reduces the pressure on the pads.
rm2001wj is offline  
post #12 of 12 Old 04-20-2009, 06:35 PM Thread Starter
Chandler
Registered User
 
Join Date: Sep 2005
Location: Chandler, Arizona
Posts: 195
I retested mine this morning on the way to work and my pedal is actually much firmer now. I do believe what is being said as my pedal as full stop will still depress. When I'm driving there was a noticeable new firmness when I braked.

2004 WJ Overland
Chandler is offline  
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the JeepForum.com forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid e-mail address for yourself.



Email Address:
OR

Log-in









Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Similar Threads
Thread Thread Starter Jeep Forums Replies Last Post
Parking brake adjustment in 01 Grand Cherokee? Bad brake shimmy too! JeepSam ZJ Grand Cherokee Forum 8 05-19-2014 06:05 PM
New calipers/brake line/pads, bled brakes, now i have no brake pressure! klwong1 ZJ Grand Cherokee Forum 13 11-16-2013 09:15 PM
Repaired leaking brake power booster, but now brake lights are on all the time MNWJ ZJ Grand Cherokee Forum 2 05-11-2009 07:59 AM
brake pedal mushy macwig52 ZJ Grand Cherokee Forum 3 03-05-2009 03:53 PM
Front brake caliper thread repair Stuart ZJ Grand Cherokee Forum 6 05-22-2007 10:40 PM

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome