Another possibility is that there is a brass piece, spring loaded, that seals against the rotating turret body. It's face can be damaged by a chip being caught there when the turret turns, eventually causing the "fountain" effect.
Remove the turret center cap, then the manifold block (4 screws) and the brass plug comes out with it. You may need to resurface the face of this brass piece.
Again, this applies if you have this particular design.
George
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)