Automotive

Help with rotor getting very hot on the rear left side.

  • Last Updated:
  • Nov 9th, 2020 3:57 pm
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Feb 16, 2003
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Help with rotor getting very hot on the rear left side.

I have a 2012 Hyundai Santa Fe Awd and last week I drove it to go to town to put new winter tires and when I got back home I noticed that the left rear side wheel was very hot.
I checked the rotor and it was unbearably hot, could not touch it.
I had the truck up for inspection the month before and it got new rotors and pads and a new caliper on the right side. But I didnt drive the truck since then until I took it to put the winter tires.

I am leaning that I should replace the caliper but the evidence confuses me on that.
The rotor does not show any wear, there is a stamp of the pads in it because I didnt drive the truck for weeks.
The pads show no wear either.
Heres what I did so far:
The wheel is not stuck, it doesn't particularly feel sticky, because its an awd it doesn't rotate freely.
I took the caliper and pads and rotor out and checked that the parking brake shoes do not show any signs of wear or that thet rubbed anything recently. Checked the parking brake line and it moves with no restriction.
Checked the bearing and there is no give, there is no sound, there is no rattling so I crossed it off as well.

The pads they are not sticky they move freely in their encasing but just to make sure I cleaned it up, used a file to clean any rust I could see and put copper anti seize. I noticed however on the inside pads in the grease that it had a bit of brake dust;
One of the caliper pins was stiffer than the other, so I took them out and cleaned them and didnt see any signs of rust. Put fresh silicone paste on them and checked that it moves easily.

The caliper piston, I used a c-clamp to push the piston and there was not much resistance for it go in or was it locked but I did notice that while I was working on the other parts the piston eventually uncompressed because when I went to put it back in I had to compress it again with the c-clamp to fit it in the pads.

Finally I bled the line for any possible air bubbles or blockage and the fluid gushed with no restrictions or bubbles.

My test drive consisted to drive the truck down the road for 2-4 kms without using the brakes and using inertia to bring it to a stop and then putting it into park.
At that point would do a check and the right rotor was cold as well the caliper and pads, the left side the rotor was slightly warm, but the caliper felt cold.
Then on the way back home I brake hard a couple times to use the brakes.
The left rotor side is impossible to touch compared to the right side.

So here is my theory based on my observations but because I am not a professional mechanic perhaps someone else has had this experience and can confirm that its the caliper.
For some reason the piston uncompresses (pulls out) enough that it makes the pad rub on the rotor, it doesn't push it hard enough to make it stick. so that friction between the pad and the rotor is enough to heat it up.


Does this sound plausible and I replace the caliper or do you suggest something else to look at?
I just want to make sure before I buy a new caliper that I am on the right track.
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May 28, 2009
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Get the car on an incline. Put in neutral. If car moves, calipers aren't sticking. If car wont move, the caliper is sticking.

Sometime taking a short test drive and hitting the brakes hard will free it up. Just dont come to a complete stop when doing it. Make sure to drive for a while to cool off brakes before stopping/shutting down.
[OP]
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FlashFyre wrote: Get the car on an incline. Put in neutral. If car moves, calipers aren't sticking. If car wont move, the caliper is sticking.

Sometime taking a short test drive and hitting the brakes hard will free it up. Just dont come to a complete stop when doing it. Make sure to drive for a while to cool off brakes before stopping/shutting down.
The caliper is not sticking. the car moves freely, it just heats up the rotors too much imo.
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Sep 4, 2006
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Ottawa
You need to remove, clean, lube and replace the caliper slides (if the piston is not stuck).
Sr. Member
Oct 21, 2006
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do the pads float freely in the caliper bracket?
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Jigsaw wrote: do the pads float freely in the caliper bracket?
Yes, they did and I even took them out and cleaned them up and and put new fresh grease just to be sure. They do not stick at all.
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jayoldschool wrote: You need to remove, clean, lube and replace the caliper slides (if the piston is not stuck).
Do you mean the pins? Yep I took them out, cleaned, checked for signs of rust, found nothing and added new silicon paste. They move freely.
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mrmccowcow wrote: Parking brake might be sticking
Not possible, I pulled the rotor out and theres no signs of any wear or been used recently.
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Oct 21, 2006
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the signs do point at that one particular caliper, for a 8-9 yr old vehicle it's not unreasonable.
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Is the parking brake using the pads or they are braking shoes like in the hat of rotor style?
If it's braking shoes, did you remove the rotor and check the inner side of the rotor?

Maybe your parking brake shoes are rubbing the inner hat even when you fully released the parking brake?
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Jigsaw wrote: the signs do point at that one particular caliper, for a 8-9 yr old vehicle it's not unreasonable.
Thats my thinking too. I am just trying to check all avenues.
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HammerJoe wrote: ....
So here is my theory based on my observations but because I am not a professional mechanic perhaps someone else has had this experience and can confirm that its the caliper.
For some reason the piston uncompresses (pulls out) enough that it makes the pad rub on the rotor, it doesn't push it hard enough to make it stick. so that friction between the pad and the rotor is enough to heat it up...
Possible bad hose - does not allow pressure to release
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l69norm wrote: Possible bad hose - does not allow pressure to release
I checked it yesterday and bled the line It gushed good.
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HammerJoe wrote: I checked it yesterday and bled the line It gushed good.
Caliper bracket?
On my Explorer, the passenger side rear brakes was sticking (known defect) and I had to file down the inside part that holds the ears of the brake pads.
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HammerJoe wrote: I checked it yesterday and bled the line It gushed good.
HammerJoe wrote: ...

The caliper piston, I used a c-clamp to push the piston and there was not much resistance for it go in or was it locked but I did notice that while I was working on the other parts the piston eventually uncompressed because when I went to put it back in I had to compress it again with the c-clamp to fit it in the pads.
..
Problem is the fluid in the caliper is still under pressure and not returning to the master cylinder, otherwise the piston can't "uncompress"/ move by itself.
The possibilities are
1) bad brake hose - it's going bad internally and acting like a check valve so brake fluid in caliper can't return back ($)
2) bad abs actuator - internal valve or seal failure ($$$$)
Last edited by l69norm on Nov 9th, 2020 9:57 am, edited 1 time in total.
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Sep 4, 2006
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Good call on the wheel bearing. If the brakes all check out and rotate freely, failing hub could certainly do it.

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