What is a common indication of a worn hydraulic pump shaft seal?

A common indication of a worn hydraulic pump shaft seal is indeed hydraulic fluid flowing from the pump drain line. As the seal deteriorates over time due to wear, heat, and exposure to hydraulic fluid, it becomes less effective at containing the fluid within the pump. This leads to leaks, which can manifest as fluid escaping from the drain line. The function of the shaft seal is critical for maintaining the pressure and fluid integrity within the hydraulic system. Thus, the presence of fluid in the drain line is a clear sign that the seal may need to be replaced to prevent further leakage and potential damage to the pump and connected components.

In contrast, increased noise from the pump, fluctuations in system pressure, and loss of hydraulic fluid through the reservoir can be indicative of other issues in the hydraulic system. Noise might arise from various operational issues, while pressure fluctuations could be related to other component failures or malfunctions. Loss of fluid through the reservoir indicates a different type of leak, likely somewhere else in the system rather than specifically from the pump seal. Therefore, identifying the specific symptom of fluid flowing from the pump drain line helps pinpoint the problem more accurately to the shaft seal itself.