i suggest you to check the piston if worn
or dry (press the pedal when brake are without pads),
you can cover the surface with teflon grease
then with 80 grit paper clean the discs and flat the
grooves if not too deep
change the brake lines with new ones
and let the old brake fluid flow out
when flow outside the brake lines new fluid
screw it on the brake (the pistons should be all inside pressed)
thight all the bolts, press the brake pedal until become hard
now you can do the break in without bleeding anything
if the brake power do not satisfy enough you have
to change the brake oring too following the same
instruction as above