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Bad brakes on a '98

N

Nomaspescado

NAXJA Forum User
Location
Lake Tahoe
Hello,
I have a '98 4.0L UpCountry with ABS, 106,000 miles.
I've only had it for 10K and it's time for new brakes.
It feels like I'm pushing down on a 2x4 and the pads and discs show they need replacing.
My question is:
What are the "signs" that a brake booster has gone bad??
I am well aware of what happens when a master cylinder goes bad and I do not think that is what's happening. I get constant pressure requiring no pumping, but it has "horrible" sensitivity as well as it requiring way too much pressure at the pedal. It feels very sluggish and slow. The ABS works great, though.
Thanks for any input from other owners out there.
Steve
 
Just to keep it near the top....

Sounds like a bad booster to me, but I've never dealt with the ABS system on these things. I do see from the 99 manual that these systems do use a normal booster (the old Renix era ones did not), so that would be my first suspect if you have a firm pedal and no other obvious problems, but too much effort.

Here's the standard test for boosters: First, with the engine off, push the pedal a few times. Does the pedal effort and height change at all, and can you hear any whooshing noises? Normally the booster should hold a couple of pushes worth of vacuum. If not, suspect a leak.

Now, with all vacuum gone from the booster, and your foot planted on the brake pedal, start the engine. If the booster is good, the pedal should sink part way down. If it doesn't, it isn't boosting.
 
On my 98 TJ the pedal is kinda stiff but the brakes are really touchy, if you use too much brakes you'll do an endo
 
Thank you, Mr.Currie.
Following your instructions with the motor off, I pressed the pedal several times. It took 3 to 4 pushes to get firm pressure (accompanied by the whooshing noises). Then, holding the pedal I started the Jeep and felt the pedal move down significantly, almost to the floor, but not touching...
Does this sound like a good brake booster and bad and/or extremely worn out brakes?
Thanks for your time :)
Steve
 
Nomaspescado said:
Thank you, Mr.Currie.
Following your instructions with the motor off, I pressed the pedal several times. It took 3 to 4 pushes to get firm pressure (accompanied by the whooshing noises). Then, holding the pedal I started the Jeep and felt the pedal move down significantly, almost to the floor, but not touching...
Does this sound like a good brake booster and bad and/or extremely worn out brakes?
Thanks for your time :)
Steve
Click to expand...

Your booster sounds fine. I guess it"s time to open up the brakes. It"s pretty common for the rear adjusters to stop adjusting, so if you haven"t had it open in a while, that"s probably a good place to start. If you haven"t had the fronts apart recently, it"s also possible for the calipers and pads to be getting rusty and not moving smoothly. Check especially the tongues on the pads where they engage with the rail on the steering knuckle. If there"s still a lot of pad left there, you can just clean them up and put them back together, and sometimes that will improve your brake feel, but if in doubt, new pads are pretty cheap.

Lacking any experience with ABS, I"m ignoring that end of things. If there is something going on with the ABS that is fouling up your braking, I am out of my depth.
 
Not sure if Jeeps are the same way but on Fords ABS is actuated at each wheel at an actuator that catches a cog on the axle shaft and it's all electronically triggered so if your XJ shares this setup then the ABS shouldn't have anything to do with your pedal.

However when the ABS engages you will feel it in the pedal, it will be stiff and will have a grinding feeling to it and there may or may not be a grinding noise.
 
Try pulling your ABS main relay (location indicated in the owner's manual) and driving it a little. This will completely disable the ABS system. If that improves it, keep it that way... The ABS screwed up on my bro's ZJ and the brakes felt horrible, but removing the abs relay made them normal. Jeep ABS sucks anyway. Oh yeah if you do this the ABS light will be on... My bro never cared but there are various ways to disable the light.
 
Thanks for the replies fellas... good advice taken.
I will replace the rotors, pads, rear shoes, and check the drums for any life left.

This brings up an important question about the ABS:
Can I do the brake job and BLEED the system like any other non - ABS system? Or, does doing this require special equipment to bleed out the ABS system?

I've read confusing responses on other threads..
Thanks all,
Steve
 
Nomaspescado said:
does doing this require special equipment to bleed out the ABS system?
Click to expand...

Actually yes it does, you must rent an ABS disarm module, the modulator puller and the lithium transducer

All you need to do is unplug the ABS wires, that's all.
 
According to the 99 manual, you need to bleed the ABS system 3 times. First, a regular "base" bleed, then the ABS system gets bled using a DRB scan tool to cycle and bleed the HCU pump and solenoids, and then another base bleed. Ugh!
 
I just found the same thing in a FSM... :(

Zoro,
Will unplugging the ABS wires enable me to do the brake bleeding without the need for all those specialized tools?
Thanks,
Steve
 
i also have bad brakes on my 98' but i dont think its the booster i DONT have abs. but i think there might be a leak in my lines cuz about every 3 to 5 days i am just about compleetly out of break fluid and i just start to pump air into the lines. when i fill it back up with brake fluid they seem to work fine.
 
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