pull the pistons out , once i pull the pistons of mehran and found that the cylinder is full of rusty oil,,,,,,,,,,also the piston polish is all gone and O ring cant able to seal it if i push the piston back,,,,,,,,,,,,,,,this happens when you replace the pads,,,,,,,,,,,new pads are thicker and you need to push the piston back,,,,,,,,,,,,,,,the portion of piston which is out side the O rings was all full of rust because the protective boot was not installed and no lubrication was there to prevent it from rusting,,,,,,,,,,,,,in this case there was no option other than to replace the whole assambly,,,,,,,,,,,,,,,
remove the bolt which holds the hyudralic line and insert a screw driver init and strike the piston from back side to strike it out,,,,,,,,,,,,some time you need a hyudralic pressure to push the piston out,,,,,,,,,for that simple remove the pads from one side and ask some one to push the pedal ,,,,,,,,,,piston will be out alone with lot of oil to waste,,,,,,,,,,,to remove the piston from the other side you have to block the hyudralic line of the first piston (which you remove already) and then press the pedal again,,,,,,,,,,,,,,,,,,,,,,this may be not posible for you ,,,,,,,,,so batter try the first one ,,,,,,,,,,,,,,,,in my case i flush the cylinder with fresh hyudralic oil with out removing the piston,,,,,,,,,,,you can clearly see the inner story of cylinder from the bolt of huudralic line,,,,,,,,,,,,,inside was not rusty so i simply flush it,,,,,,,,,,,,
