CryptiC

Well its my parents jeep and i am trying to help them.

Any info/ideas is appreciated..

I was driving the jeep and all the sudden when I pressed on the brakes the abs kicked in started rapidly tapping against the pedal and making a loud grinding noise which sounded like it was coming from the bottom of the jeep.

When ever I even slightly touched the brake pedal while this was happening... the brakes would lock up fully.

Obviously my first reaction was lolwtf , but then I've been trying to figure it out..its been happening alot.. the noise will come on while driving and anytime the noise is going the brakes instantly lock up..

ABS sensor maybe?, maybe Brake lines or something? I don't know too much about mechanics, I know my fair share..but have never seen this... and for some reason my dad thinks this is the pistons locking up.. and with my knowledge I can't see that even being a possibility.

Thanks in advance,
-CryptiC

RRAM

sounds very much like calipers are sticking. What shape are the pads in? if there metal on metal they will screech and lock up too.

jpcounty69

I have a 94 GC doing exactly the same thing more and more often. ABS will kick in and run/hum/vibrate randomly and I need to tap the brake pedal several times to make it stop. Loud pumping/vibrating noise and nobody can figure out the problem. HELP!!

stomper27

Is your ABS warning light on?

For about $90 the stealership will tell you what's wrong. You don't want your parents brakes to lock up on the road.

pwb

I have same too, the ABS kick inn if i turn rigth (full turn) at slow speed without touching the breakes or if i breake when the speed is low. After cleaning the tonewheel it was a litle bit better, but its starting to get back more and more. Have you tried to remove the fuse for the ABS pump to see if its realy the ABS ?

jpcounty69

I should clarify that my brakes don't lock up when this happens. Actually the opposite happens in which it's difficult to come to a complete stop when the pump is running and pedal is vibrating. The pedal gets very difficult to press down while it's vibrating and I have to try and tap the pedal several times strongly to get it to stop running/vibrating.

My ABS light does not come on whenever this happens and I have also thought about just disconnecting the fuse and see if this problem will quit without affecting anything else.

Can somone also clarify if the ABS on my 94 Grand Cherokee only operates on the front disc brakes? Is that where any sensors would be located at? Are the rear drum brakes part of the ABS system as well and/or is there any sensors located within the drum brake assembly?

The reason for my asking is that all this appeared to start happening at the same time a local tire shop changed my wheels to studded tires and had to replace a stud they broke on a rear wheel. They looked things over a couple of times and told me that this problem had to be a coinsidence and from nothing they could have done changing a rear wheel stud. They even put my original wheels back on and the same problem now continues.

pwb

A litle update on my ABS trouble. When i got my ZJ the one of the drum brakes was loose and it had moved a litle on one of the ABS sensors. When i replaced one of my axle this summer i moved it in place and its ok :-) it was maybe 0,5mm off, but now its in place and i dont have the ABS problem anymore :-)