Urgent: RPM dependent squeal and 'braking' from rear

I'm in desert west texas atm, and I have a problem where the Jeep cold starts and drives fine, but after 10-20 miles I'm getting a wheel RPM dependent squeal once per revolution as the car slows to 10ish MPH. This gets worse as the car heats up. There is also a noticeable braking effect with the noise, as if tapping the brake each time. I've taken it to a mechanic but they're saying nothing looks wrong with it. I'm changing the wheel bearings out just because I had the parts in my road bag, but need to figure this out as I have 700 miles left in the trip and don't want it failing outright or catching fire.

What should I be looking at? Drum brake adjusters? If so how (will be searching the forums concurrently).

1998 XJ AX-15

Warped rotor or hanging drum. Feel the heat coming off each corner after driving for a while and look further into whichever one is hotter.

You are doing better than me a couple years ago. In west Texas hauling a load when I was a hotshot driver I cracked a piston in my 6.5 diesel.

Pull pads and look for something embedded in them. It could even be some foreign material that got included in the pads when they were manufactured. Or it could be some foreign object that got picked up, like a tossed bit of sand. Look at the rear shoes with the same eye for something foreign.

It will be easier to diagnose if you can pin down which wheel is doing this.

Make sure your calipers can slide properly on their pins as well as on the knuckles. Make sure your shoes can move properly on their backing plates. I have not seen such severe results, but front pads and rear shoes will wear grooves into the knuckles and backing plates respectively. If you were to combine those grooves with a bit of runout on either rotors or drums you could conceivably get the symptoms you are having. There are special lubricants for use on these points in brake systems. White Lithium grease will work on the drums, but cannot handle the temps for the discs. Note that it is a minimal amount of grease used. You do not want to get it on any of the friction material.

Best of luck and let us know what you find.

Unclewolverine said:

Warped rotor or hanging drum. Feel the heat coming off each corner after driving for a while and look further into whichever one is hotter.

You are doing better than me a couple years ago. In west Texas hauling a load when I was a hotshot driver I cracked a piston in my 6.5 diesel.

Click to expand...

Finally convinced the mechanic that the issue was the rear right drum brake, after he spent the day chasing a transmission or transfer case rattle (which may be another issue for another day). Had him replace the drum and in testing it after that he did find the right drum hotter than the left. He wants to replace the wheel cylinder (maybe found that it wasn't retracting, bit of a language barrier and only mrs. tonic speaks good spanish but doesn't speak good car). Finger's crossed that's it, as the nearest manual transmission shop is El Paso 240 miles away. Barring that hoping to throw the Jeep on a U-Haul car trailer to tow it back home.

Front pads will wear a severe groove where they ride, just had to weld mine up and grind them back smooth. Caused a considerable squeal that drove me nuts even after new pads and rotors.

I just realized you are driving a manual, bet you dollars to donuts your e brake cable is hanging up on the right side. Never seen a brake cylinder hang up but seen tons of frozen and sticking parking brake cables!

Thanks UncleW. How do I check for that? It's definitely the rear drums, not the front discs. Will it hang up inside the drum brake or near the adjuster box? I don't get the sense that the shop I'm in has a lot of experience with this stuff... If I find anything is there something I can do on it? Lube?

It will hang up in the flexible sheath coming down from bracket by the handle to where it goes into the backing plate, usually spraying pb blaster or wd 40 in both ends and working it in and out will free it up. Jack it up, Engage the brake, then release it and try to turn the tires by hand I bet the right one is stiff or doesn't move at all. Sometimes you can stick a screwdriver in the adjuster hole and pry the adjuster arm forward so it un sticks, not sure if you can do it on an xj. If you get it to a point where it doesn't drag just don't use the parking brake again until you are done with your trip and have some time to deal with it. Best of luck, hope you don't have to change it, parking brake cables are a major pain in the butt to replace.

Alright, good info. Will try that tomorrow.

In the end, replaced the drum, the wheel cylinder, tried lubing the parking brake cable, and manually adjusted the pads a couple clicks back. No issue in the 400 miles driven yesterday. I'm deliberately avoiding triggering the self-adjuster until I'm back in town.

Glad you aren't having to tow it home.

The sticking e-brake cable is a good tip. It has been a long time, but I helped a friend deal with that on a Ford Maverick. If rust gets started in one of those cable assemblies it will mess things up.

If it turns out you need to replace the parking brake cable, the aspect that I have found to be the most challenging is trying to get all three of the little tabs depressed at once so you can pull it backwards out of the hole. I have found that roll cutting a piece of 1/2" copper pipe results in a workable tool. Roll cutting (just a typical plumber's copper pipe cutter) reduces the I.D., and the reamer that is built into the pipe cutter opens it back up. This allows you to fine tune the fit to get just the right compression on those tabs.

I have used a small box-end 12 point wrench on those parking cable
tabs. Usually a 7/16" or 1/2" wrench will compress the tabs
enough to release the cable.