Ducati Diavel Workshop Manual page 621

Cooling system: coolant expansion tank
Fit the clip (8) on the hose (7).
Insert completely the hose (7) into the lower fitting (D) of the expansion reservoir (12), by orienting it so as the reference
(E) of the hose matches with the arrow in relief (F) on the expansion reservoir.
Note
In case of difficulties during insertion of the hose (7) into the fitting (D) it is recommended to apply lubricant suitable for
rubber to the fitting.
Orient the clamp (8) as indicated and bring it in correspondence with the area (G) of the hose (7).
Tighten the clip (7).
Fit the clip (19) on the hose (20).
Insert completely the hose (20) on the upper fitting (H) of the expansion reservoir (5), so that the straight part (l) of the
hose is parallel to the bracket (2) as highlighted by the axes (L) and (M).