Check to make sure you have enough oil in your Gear Boxes. You also need to do some oil analysis from time to time to check for wear and foreign particulates. Check your seals to see if they are leaking. Examine backlash and endplay to make sure all shafts, gears, and hardware are working correctly.
Structural components are also areas of great concern. Older Cooling Towers often have aging wood components, whether it be structural, stairways, walk ways, etc. Deteriorating framework and wood members can cause serious problems if left unaddressed. Loose or missing bolts and fasteners are an indication of an accident just waiting to happen
It is vitally important to check nozzles that might be plugged along with your pipes. These should be inspected and cleaned on a regular basis if needed. It is important to have good water distribution over the entire tower. Nozzles, whether in up-spray or down-spray mode, should be checked to see if they are spaced and operating effectively.