If brake controls feel “spongy” due to the presence of air bubbles in the system, bleed as usual, as described under Section
"Changing the brake system fluid".
Before bleeding a brake master cylinder, move back the calliper pistons to let any air build-up in the ABS control unit flow
into the master cylinder; as described under (Filling the brake system).
Purge must be carried out by means of the corresponding unions (A) placed on the callipers and the brake master cylinders.
If the ABS hydraulic control unit has been replaced, it will be supplied with the secondary circuit already filled with fluid.
Control unit must thus be assembled and the system filled and drained as a traditional system.