Randomly one day my brakes started squealing or screaming a single note RIGHT before I came to a complete stop. Leading up to the single sustained note, I hear a couple squeaks, same note(one per rotation of the wheel) and the brakes kind of grab and let go in time with the squeak until the sustained note. I still have great braking power through all of this. After getting a diagnosis, I replaced the front rotors (my brake pads were still in great shape). The sound was still there. Then I replaced the front pads, and the sound remained. Also, after sitting at a long stop light, when I release the brake, a different lower note "sings" until I move faster (seems to be until the wheel goes around once). I have "bedded" my brakes and it didn't help at all. My hub assembly is going out on my front driver's side wheel but am not sure if this could be contributing. I don't know what else it could be, but it's very loud and very annoying/embarrasing. HELP!!!

 

Bled

Hi. A good start here would be to jack it up and spin the wheel (s) and see if they are free, (mostly). Also test it for looseness. Wiggle it from the 9 and 3 positions, as well as 12 and 6. Sometimes I'll put my knees against it to really get some leverage. Hopefully you will find something loose or sticking. Don

 

I'm not an expert, but I think squealing comes from glazed pads. Could you have a caliper that's not releasing? Also, if there is a groove worn into the rail that the pads sit on (part of the steering knuckle), it could restrict pad movement/release.

 

We replaced them with the same sound. They aren't glazed.

 

OK. I had a situation with a constant pulsing squeal (no brakes engaged). With brakes engaged, it got quieter until the jeep was traveling under 10 mph, at that point it would turn into a constant squeal. I replaced pads and rotors, and it still came back after a month or so. I think I have a groove in the knuckle. That's why I mentioned it. Could very well be something else for you.

 

Okay thanks! How do/did you fix it?

 

You should pull the wheels off and make sure that this could be your problem. Each set of pads are guided by two rails as they slide in and out. These rails are protruding parts of the steering knuckle (the caliper bolts to this also). Over time, the pads can wear a groove into the rails, which can eventually become a sticking point for the pads. I think there is supposed to be a specific amount of clearance between the pad and rail. That's why some pads ship with clips that vary in size (they are meant to fill that space). If the clearance is off, you can get squeal. If there is a groove, the clearance is off, and the pads might be sticking.

Look for a groove or too much play in the pads. You will probably need to take the caliper off to see a groove.

http://tinyurl.com/4xtf8zp
In the picture, the rails are what the knuckle is being held by.
Photos of knuckles:http://tinyurl.com/3fjb9xa

If there is a groove, you have two options: repair or replace. You can probably get decent knuckles at the local JY. Otherwise, they're pretty expensive new. As for repair, some people have welded metal into the groove, and filed/grinded it to shape.
See writeup:http://www.jeepforum.com/forum/f9/xj...rooves-924713/

 

Also a great brake writeup with photos:https://www.cherokeeforum.com/f51/ba...t-brakes-7143/
Possibly related thread:https://www.cherokeeforum.com/f2/fro...1-300-a-94538/

 

The rails can also be warped (not parallel). Also, measure the clearance and see how close it is to the recommended. Every XJ is different, so many people never use the clips and have no problems. I'm one of them, but the groove got me.

 

Do you still have the disc brake pad clips at the top and bottom of your pads? The reason I asked is because my 91 had these when I bought it. I figured out that these clips were rubbing on the edge of the rotors causing this gawd awful noise. Being new to my Jeep at that time I figured it was a wear indicator of some sort so I put brand new pads on it. When the noise continued I bent them in every kind of direction I could think of they still squealed. So, I bought new clips. The new clips squealed. After looking the pad and caliper mounting setup over really good I realized these stupid clips had nothing to do with the security and proper operation of the brakes. So, I removed the clips from both sides and threw them in the trash. I've been driving my Jeep on and off road like this for 5+ years and the brakes work perfect....AND NO MORE SQUEALING since!!!

 

This is why I don't use them either.