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I had noticed a burning smell in my right rear brake, suspected caliper issues, and I decided to do a brake job (2009 Mercury Milan).

After thwacking off the tightened caliper with a hammer and finishing replacing the pads, I decided to use a brake caliper tool (item 648622 at Advanced Auto) just to see if I could move the old piston back.

Well, I could push the piston in with the screw tool fairly easily, and I pushed it the whole way in and decided to try just putting the old caliper back on and testing my brakes. Unfortunately, I noticed immediately that the brakes gripped harder and harder while my wife repeatedly depressed and released the pedal. The brake pads feel like they've got considerable resistance even with the pedal released.

My question: can a brake caliper that can be pushed in with a tool still be considered bad/seized??

Or do I have another issue?

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  • No idea about a Mercury Milan, but on any car where I have serviced the brakes, you should be able to push the piston in with your fingers, without needing a tool. I would guess the piston is partially seized.
    – alephzero
    Sep 18, 2021 at 23:00
  • Does your rear caliper also have the emergency brake built into it? The piston has to be rotated as it is pushed back in with the special tool?
    – HandyHowie
    Sep 19, 2021 at 7:00
  • @handyhowie yes and yes
    – theforestecologist
    Sep 19, 2021 at 14:51
  • Maybe the lever that connects the emergency brake cable to the caliper is seized. I have seen that occur before.
    – HandyHowie
    Sep 19, 2021 at 15:16
  • I had considered that, too. I watched as the e break was engaged and disengaged, and it appears everything is functioning properly.
    – theforestecologist
    Sep 19, 2021 at 18:47

2 Answers 2

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The photos I see on the internet show that your calliper has a piston on only one side. If the piston is free, then it is more likely that the fault is a seized slider mechanism that centres the calliper on the disc/rotor.

The frame the calliper bolts to has 2 metal sliding pins inside rubber dust covers. You should be able to move these metal pins freely in and out of the frame. If these seize, the brake pad that doesn’t have the calliper piston pushing against it can be permanently pushing against the brake rotor/disc.

Check that these pins are free. It they are seized, you may be able to coax them out and clean and grease them.

You can see the pins inside the rubber covers at the top left and right of this this example photo below.

enter image description here

I got this photo from here - https://www.autozone.com/brakes-and-traction-control/brake-caliper-front/mercury/milan/2009

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  • Thanks for the answer. These actually move quite well actually!
    – theforestecologist
    Sep 19, 2021 at 14:50
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A brake caliper piston can possibly sieze at certain times and places where the cylinder may be corroded even if the piston manually pushes back. But usually if you don't have to use much force with the tool to push it back then the caliper may be good. A common problem that causes your symptoms is a bad rubber brake hose. Due to internal damage in the hose, it allows fluid pressure to activate the brakes but blocks the pressure to release when the brake pedal is released. The way to check this is: when your wife pumps the brakes up and the rotor doesn't turn after she lets up on the pedal, loosen the caliper bleed screw until fluid comes out. After fluid pressure is relieved if you can then turn the rotor, then it's most likely a bad brake hose. When replacing a brake hose it is highly recommended to change all four.

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  • I had considered the hose, but I figured since I could push the caliper in with the screw tool, the hose had to be working. Is it possible that I can overcome an otherwise compressed hose using the screw tool?
    – theforestecologist
    Sep 19, 2021 at 0:27
  • theforestecologist. Good point. If the piston had unusually high resistance, then yes, you could overcome hose blockage. But I would look to @handyhowies answer for the most likely cause at this point. Unless there was unusually high resistance.
    – Jupiter
    Sep 19, 2021 at 11:26

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