Ducati Diavel Workshop Manual page 76

Maintenance operations
Unscrew the cap (6) of the rear brake fluid reservoir (7).
Siphon off the fluid from the reservoir (7).
Fill the reservoir (7) with new brake fluid up to the MAX. mark.
Press the pedal to allow the circuit to go under pressure.
Keep the pedal pressed to the bottom.
Loosen the bleed valve (8) to allow fluid to escape.
The pedal is at the end of the stroke in lower position.
At this point, tighten the bleed valve (8) to the specific torque of 23 Nm ±10% (Sect. 3 - 3, Frame torque settings) and
release the pedal; press the pedal.
Repeat the operation described above until the old fluid flows completely.
Warning
After eliminating the old fluid from the tank, during the refilling operation always keep the oil level above the MIN mark to
prevent the formation of air bubbles inside the circuit.