CherokeeSailor

My jeep stays parked a few hundred feet from the Gulf of Mexico for a couple days at a time, so rust happens fast. I went to rotate my tires today and noticed this:



Looks like my pad has been making contact the whole time it was sitting for two days, I'd imagine it's pretty safe to assume it's doing that while I drive too?

DFlintstone

Curious, what year is it? A sure no fail test of a caliper dragging and not releasing the rotor is it will get hot. Pretty hot pretty fast. If you stick your finger in there on the rotor you might hear and smell it burning before you feel it.

CherokeeSailor

It's a 99, with ABS, I'll have to test it out tomorrow to see about the heat

kstopp

That's pretty standard, I don't think you have any issues. I get that occurring on all of my vehicles that don't get daily driven.

CherokeeSailor

The rust is standard, sure, but is the imprint of the brake pad?

nujeepguy

i drive a mile without touching brakes. coast to a stop ,get out and do the finger hot test!
anytime i stop on a hill/grade i shift to neutral. should drift right away,no drag.
in a pinto yrs ago i didnt move!, hot caliper. it was a flex hose that closed up,not the caliper.

kstopp

Yeah the imprint of the brake pad is what I was referring to. The pads will always be lightly scuffing the surface of the rotor. When you park the pad shields moisture from forming on the rotor surface and you get rust everywhere else except that area.

CherokeeSailor

I appreciate all the input, I plan to check the heat coming off each side tomorrow after driving, I'll come back with my findings, and Kstopp, that's pretty reassuring, thanks

nujeepguy

ideally the pads retract slightly and dont touch

bad_idea

What causes the pads to retract?

As others have stated, the pad is always riding against the rotor. Normal. I had a caliper stick on my 90 XJ. It got so hot smoke started coming off of the wheel and the Jeep would noticeably slow down when let off the gas.

diskman

There is a rubber square O-ring that seals the caliper cylinder and piston. The O-ring is the part that causes the piston to retract in a functioning caliper. Over time, corrosion from moisture builds up behind the o-ring groove causing the piston to "hang". Can be repaired if not TOO corroded with a good cleaning of the groove and a new o-ring. Or just replace the whole caliper assembly.

CherokeeSailor

Well, I measured the temps of the face of the disc brakes today after my normal commute home from work, the passenger side was around 230, the driver's side(pictured above) was about 260.

nujeepguy

u gotta do it w/o touching the pedal, coast to a stop

then if hot u got a drag

DFlintstone

Agreed^. You would expect them to be hot if you used them. That said your temps seem pretty high. Today coming home I had an opportunity to leave (work) cold, then drive two miles at 50 something, then stop with just a little assist from the E-brake. whip out the laser deal, and read really close to 80*F on both sides.

I joined the forum in 2011 over this. A trip coming up and dragging brakes. Had I had the time I could have ordered rings to replace the swollen ones in my calipers. Instead I needed to turn in my OEM calipers for whatever they had......Not terribly spendy and easy as it gets.

It seems unlikely both flex lines failed for you to get drag on both sides. To test potential residual pressure one might loosen the bleeders and check for resistance on stands right in the driveway.

The maybe answer earlier questions, "what makes them retract?" Me thinks the hub bearings have some small amount of play letting the rotor "randomly bash" the piston back a tad in the caliper. Yes there should be very little play in the tire/wheel/rotor, but here just a couple thousandth's would prevent even light contact.

Here in my first post/thread in 2011, I end around post #16 stating, "with a good heave I get 1-1/2 revs on the wheel".. https://www.cherokeeforum.com/f2/dis...o-much-100670/

nujeepguy

the square "o'ring was explained in a service manual i had back in the 70's.
it flexed and pulled back. then the piston would slide slightly when needed to self adjust as pads wore down,neat idea...