How do you change rear brake pads and depress the piston on an Audi A3?

Answer 1

Do only one side at a time. Undo brake fluid reservoir filler cap and keep an eye on the fluid level through the process. Remember to replace the cap at the end. Release hand brake. Chock the wheels. Use jack stands and all the usual safety precautions. Remove the wheel.

Caliper comes apart with two bolts from the inside of the assembly like most.

Careful with the sensor wires and brake fluid hoses. Remove old Pads.

Piston must turn clockwise as you push in the piston, in order to get the new pads and caliper back on the disk rotor. A universal six sided tool which fits on a 3/8 square drive ratchet, locates in the slots in the piston to make this easier. There is also a special Audi tool, but the universal one works as well. Purchase from auto shop. Can be done (sometimes) with circlip pointy nose pliers, but quite difficult.

Turn clockwise as you push in the piston. Watch the fluid level in the reservoir as you do it. Once completely bottomed in the housing you are ready to replace the pads and bolt the caliper back together.

Use silicon paste to lubricate and anti seize in hot moving parts.

Place the cap back on the fluid filler and test one side at a time by depressing the brake pedal a dozen times until everything seats. Check fluid level. Do the other side.