Most likely your viscous fan clutch is worn.
The new upgraded ones only fit with a new fan and pulley, check before you buy it.
There are treads on this forum about refilling the clutch with silicone, never tried this myself.

First check if your radiator gets hot, if not the thermostat is bad. The clutch gets its heat from the radiator. If the radiator not get water from the engine the clutch will not engage.

Rob