Steve,
There are two hoses to each slide cylinder, and one hose is pressurized under extension and one is pressurized under retraction with the corresponding hose being vented to the fluid return in the fluid reservoir when either hose is pressurized for movement. Since the hydraulic hose will move when it is under full pressure, you can determine which hose is leaking by just moving the slide, and watching or feeling the hose, but be careful as a pin hole in a hose at 3,000 PSI can penetrate the skin.
The other way to determine if it is the extension or retraction hose if you know which slide it is going to is to slightly loosen the hose, since the extension hose will have residual pressure when the slide is extended and the retraction hose will have pressure when the slide is retracted.
Gerald