Cars braking system problem?

i have a 98 peugeot 306 1.4 and the brakes are soft the front calipers were seized so i unseized them and replaced the pad and bled both lines then i checked the rear drums and the pad were fine so i tightened them abit and bled the lines it made a little difference but not much,will i need to replace the master cylinder?also would it make a difference to bleed the master cylinder when its on the car?