[From the Shimano Tech Seminar on bleeding brakes]
Syringe Bleed -
Attach bleed syringe to the bleed valve on the disc brake calipers.
Attach the bleed funnel to the bleed port on the brake lever.
Pull brake lever & open and close bleed valve - shoots air in the valve into the bleed syringe.
Push in about of a 1/3 of a syringe of brake fluid at a time. Cycle the brake lever slowly to get bubbles out. Cycling the brake lever too fast tends to break up air bubbles into many smaller bubbles which are more difficult to get out.
Don't try to back pressure air out of the brake valve by pulling air out with the bleed syringe. This may actually introduce air into the system.
Don't overfill the system:
- Caliper piston seals are permanently flexed and can let dirt in more easily, fluid will come out of the weeping port at the lever.
- Orient bleed valve at the top to facilitate getting air out. Move caliper and brake levers around while cycling brake lever to help get air out.