it needs to be taken apart and cleaned if possible if not you have to replace the entire caliper it is most likely seized in rust
To retract the rear brake caliper piston, you typically need to use a brake caliper tool or a C-clamp. First, remove the caliper from the bracket and ensure the brake fluid reservoir cap is loosened to prevent pressure buildup. Then, either compress the piston gently with the tool or use the C-clamp to push it back in, ensuring you do so evenly to avoid damaging the piston. Always check for any rust or debris in the caliper before reassembling.
Correct tool to use Brake Caliper Piston Rewind Tool A lot of pistons easily go back in using a lever or pair of large oil filter pliers just take care not to damage piston seals and not to damage the caliper surface.
on the caliper take out the bottom bolt, there are two bolts that the caliper slides on and only undo the bottom one. Then the caliper will swing up and allow access to the disc pads . You need to get a G-clamp and push the piston in the caliper back( or else it wont fit back down). put it back together and pump the brakes to set the brake piston b4 you drive or the first time you go to brake you wont have any.
open the bleeder valve I'm assuming your talking about a disk brake, you need to use a C clamp and the old brake pads to force the piston back into the caliper. If it had a X in the head of the piston you need to get the tool to turn it back in. If all that doesn't work, the caliper is frozen and it needs to be replaced
If it has come out completely, lubricate the disc brake piston and the piston bore (in the caliper) with clean brake fluid. Make sure the dust boot is clean and is seated in the caliper. Using a turning motion (back & forth), roll the lip of the dust boot over the piston and push the piston into the caliper by hand as far as you can go. You'll need a c-clamp and a block of wood (or an old brake pad) so that you can push the piston all the way into the bore. Go slowly as you are pushing and keep an eye on the piston so that it goes in straight with no resistance. You don't want to damage the sides of the piston. If the piston goes to the bottom with no problem, seat the dust boot lip into the piston groove. You'll have to bleed the brakes once the pads are in and the caliper is reinstalled.
Not completly off, you will be able to lift the caliper off, but it will still be connected to the brake-fluid hose ;) then you pop off the pads and twist back the brake piston, and There you go :)
Jack up truck , put stands under it for safety and then pull the wheels off . Use a short pry bar to squeeze the piston on the brake caliper in a bit . Then remove the two hex head bolts that hold the caliper in place .Lift the caliper off the rotor and remove the old pads . Use a bigger C- clamp to compress the caliper piston in all the way so you have room for the new pads to slide back over the rotor .Put caliper back on and your ready to go .Once you have done both sides and have the wheels back on , pump the brake pedal to push out the piston on the caliper .
Front caliper pistons can be compressed by hand using a clamp on the old brake pad, etc. Rear caliper pistons on this model Mustang need to be "twisted" back into place using a special tool. Go to your local parts tool and ask for brake caliper reset tool and they should know what you mean. The idea here is that you use the special tool to turn the piston while applying force to push it back.
Make sure the cap is off of the brake master cylinder. You can use a tool designed to move the caliper or a c-clamp. If the piston is too far out it may not go back into the caliper.
You need to buy a c clamp one that can open atleast 6 inches take the old brake pad place it back in the way it was in there then there should be a screw on the caliper losen the screw just a little bit then put the c clamp over the brake caliper one end of the c clamp on the old brake pad the other end on the back of the caliper then tight c clamp till the caliper piston is flush with the caliper note when you thighten the c clamp brake fluid will come out of the screw that you losend so after you do all that spary some brake cleaner on your caliper rotor then put your new brake pads on add some brake fluid if needed the your ready to go
According to your question I am assuming you are talking about the brake caliper. If so take the lid off of the the master cylinder. (where you put the brake fluid.) use your old brake pad and you will need a C-Clamp. Put the C-Clamp in the center of the old brake pad and tighten the clamp until the caliper piston can't go back any further. Put the new brakes on go back with installation. NOTE> DO NOT push the brake pedal while the top of the Master Cylinder lid is off. PUt The lid on then you can hit the brake pedal.
Once you take the caliper off , you will need a C-clamp to compress the piston back into the caliper . Make sure you leave the old pad on top of the piston to help it go straight back into the housing , be careful and do not let the piston go in crooked , it will get stuck . You may also need to get a small kit , that has the little springs that hold the retaining pins in , if you break one .