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Discussion Starter · #1 ·
Jeep Sahara Unlimited:
- w/ 6-speed manual transmission, open rear, 3.73 towing package, stock, no mods, 75,000 miles, never off-roaded (...yet).

Got out of the Jeep one day and noticed a smell that led me to a very hot left rear wheel and rotor - the other 3 wheels and the rotors were cool. Took a look at the left rear caliper and these pads were worn heavily and rusted very badly from heat. It did not look like the same condition as the other three wheels. With a lot of effort, the pads were clamped to the rotor, I removed the caliper. I could not push the caliper piston in. I removed the caliper from the hydraulic line I still could not push the piston in with the pusher tool. The caliper piston was definitely seized!!

Seems like a no-brainer brake job, right?? So, I bought a new Mopar caliper. Installed the new caliper, new brake pads, new rotor & bled all four lines. Just to verify, with brake fluid in the new caliper, the piston moved freely as expected. Installed new abutment clips, Sil-Glyde greased the slider pins and clips. Brake pads opened, the caliper slides easily on the pins when installed. Pumped the brakes, the pads grabbed. Released the brake and the wheels moved freely. ... nothing out of the ordinary ...a simple brake pad swap.

Buttoned up the "brake job" took the Jeep for a quick spin everything seemed OK. Later took the Jeep for a normal drive and the left rear brake rotor and wheel surface are hot, the right rear wheel is warm while the front rotor and wheels are cool to the touch. ???? Now, no matter where I go as long as there is no hard usage of the brakes, the rear [solid] rotors are always warmer than the front [vented] rotors. I don't think the venting would have that much affect given how much I use the brakes under these situations I am experiencing.

There are many times where the rear rotors are very warm compared to the front rotors. But, every time the rears are warmer than the fronts, the left rear is always much hotter that the right rear. All I have to do is drive a 1/4 mile and the rear rotors are warm while the front rotors are still "ice cold."

I have adjusted the parking brake to the point it does no braking to remove it from the equation. There is excessive brake dust on the rear wheels but much more on the left rear wheel. The fronts hardly have any brake dust. No faults codes, no dash "idiot lights" ever. I have turned off ESP, pulled the ABS fuse, pump fuse and the rears still heat up.

I never use the Hill Assist feature so I do not have any experience on how this actually feels like when it operates. (I get the concept, but that is it.) So, I turned that setting on. While on a hill at a stop sign it takes a bit of throttle to brake the Jeep free from the "hill assist grab." When it does break free it is very noticeable release - a bit abrupt. So much I cannot imagine any body using this feature! Is this a hint to my problem??

I'm stumped!! What could possibly cause the left rear caliper to clamp onto the rotor without the brake pedal to the point of the rotor getting so hot?!

Might be related...

See also my thread on my brakes breaking me: https://www.jeepforum.com/forum/f96/brake-pedal-floor-booster-master-cylinder-4317757/
 

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thoughts-

Any codes esp ABS - confirm the ABS brake light comes on at engine start for a bulb check each start of day?

next is the flex hose to caliper...

Maybe try this - brake caliper is dragging open the bleeder did pressurized fluid blow out of bleeder?
 

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This is likely normal. I just installed my 4th set of rear brakes. 104K miles. Ive only done fronts twice. The Brake bias in a JK is toward the rear. In normal everyday conditions most of the braking (Ive heard 60/40) is rear brakes. A Jk has active ESP that is working even when the light isnt on on the dash. And most of that is done in the rear. This is one of the reasons why both the Teraflex and Dynatrac big brake kits have larger rear rotors than fronts. These rear calipers are smaller, the pads are smaller so when they do most of the braking, they are going to wear faster, get hotter, etc. The E brake is also constantly in contact with the rotor hat... the rears will by nature run hotter than the fronts.



If you had a seized caliper, you were right to change it. All good there. I'd just keep an eye on it. Hopefully you changed pads and rotors if the pad was worn to the shoe. You really should change pads and rotors every time for the rears. The front have more material so can be turned and have a longer life if you have a quality rotor, but the rear rotors... even on the big brakes, are throw aways. I've been averaging about 35K per set of rears. My factory made it 25K. Second set made it 40K (ceramic autozone), my last set was the Teraflex rear rotors, with Wagner OEX... 35K but also have had 37s and wheeled hard in that time. My recent pad change was new rotors and EBC green stuff XD. We'll see how they go? Probably the same. haha!



As long as it stops evenly, and isnt pulling to one side or the other when you are stopping, yourein good shape. Owning a JK you'll get real good at doing brakes.
 

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Discussion Starter · #4 ·
thoughts-

Any codes esp ABS - confirm the ABS brake light comes on at engine start for a bulb check each start of day?
next is the flex hose to caliper...
Maybe try this - brake caliper is dragging open the bleeder did pressurized fluid blow out of bleeder?
Dash bulb-test OK.

I've read that many people and I have heard it to by people explaining that the hose when it fails internally it can hold pressure. I don't understand this phenomenon in the way it was explained to me but I figured it was a thing from the 1970's/80's made parts. I may be guilty of swapping out this hose for no other reason. I just hope its not a master cylinder or worse, a ABS pump module that is holding the pressure.

I'll give the bleeder a look too.

This is likely normal. I just installed my 4th set of rear brakes. 104K miles. Ive only done fronts twice. The Brake bias in a JK is toward the rear. In normal everyday conditions most of the braking (Ive heard 60/40) is rear brakes. A Jk has active ESP that is working even when the light isnt on on the dash. And most of that is done in the rear. This is one of the reasons why both the Teraflex and Dynatrac big brake kits have larger rear rotors than fronts. These rear calipers are smaller, the pads are smaller so when they do most of the braking, they are going to wear faster, get hotter, etc. The E brake is also constantly in contact with the rotor hat... the rears will by nature run hotter than the fronts.
...
As long as it stops evenly, and isnt pulling to one side or the other when you are stopping, yourein good shape. Owning a JK you'll get real good at doing brakes.
I just find it hard to believe this would be considered "normal" for a vehicle. This is happening to the same corner (left rear) as the original caliper that seized and it is continuing to be the only one that gets very hot compared to the other corners. It stops fine though.

Thanks for the responses.

I'm reluctant to take it to the dealer for fear they will be "throwing parts at the problem" with me funding the "diagnostics."

Questions:

- Is it possible for the master cylinder to hold pressure in the line?
If so, I would think that issue would be happening to both rear wheels because there are only two lines coming out of it - front line and rear line.

- Is it possible that the ABS module is holding the pressure in the line?
This has 4 lines coming out of it. Possible that the Left Rear channel/output has failed in some way?
 

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If the ABS held pressure the suggestion about opening bleeder to observe if pressurized fluid is spit out would help with checking hydraulic or mechanical reason for seizing.
 

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Discussion Starter · #6 ·
I agree. I was wondering if the ABS unit was capable of causing/holding a pressure condition while the pump was not running.
 

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Discussion Starter · #7 ·
Recap: original Jeep caliper failed, overheating the brakes. Installed a MOPAR/Chrysler rebuilt replacement caliper and that wheel would get hot all the time.



Bought a replacement hose for the possibility that the hose was "check-valving." Cracked the bleeder no brake fluid spray. Took caliper off the hose to push the piston in. With the caliper off the car, on a workbench, the piston was a bit hard to push it in but it did move. I had a hunch that this much compression force might not be not be normal. I don't have a lot of hands-on experience identifying hints to failing brake components. I have been lucky as all of my previous brake jobs have been textbook-routine simple. The original caliper that failed would not budge at all. At that point I thought all of this should have been a no-brainer repair.



Anyway, I installed the new hose and reinstalled this questionable replacement caliper. Took it for a test drive, same results. This same caliper got very hot again while all the others were at ambient temperature. Reminder, the original Jeep OE caliper failed, the MOPAR replacement caliper failed. No more MOPAR for this job. I installed a new Raybestos Opti-Cat (not rebuilt) caliper. This piston moved in smoothly as expected. Took it for a test drive ... all is good again!
 

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SJ, not sure if you are still dealing with this but I've had some similar issues with my brakes (calipers seizing to rotor) as well. My jeep is a 14 with about 60k miles. I've already replaced my rear calipers and will be replacing my front calipers next week. The new rear calipers fixed my issue in the rear at least. Now I have to do the front.


I have the Dynatrac pro-grip kit on mine which replaces the rotors/brackets/pads but from my experience, the caliper/s is the part that has been the cause of my issues. I attribute some of that to the type of driving I do. Stop & Go driving, unfortunately, is how my jeep has accumulated the majority of its miles.
 
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