The SNS superconducting linac consists of 81 superconducting RF (SRF) cavities placed in 23 cryomodules, accelerating the H- beam from 186 MeV to 1 GeV. Its reliable operation plays an important role in delivering a 1.4 MW beam power on the target. A high availability of 99% has been routinely achieved in the SNS SRF systems. With its current accelerator upgrade to a beam power capable of 2.8 MW and the planned addition of a second target station, many more years of scientific life are foreseen at SNS. To sustain the excellent availability track record, a major effort is now focused on the aging effect of existing components in the SRF linac. In this contribution, we will describe a new method being developed for in-situ leak detection in cryomodule isolation gate valves. Ensuring their reliability and integrity is critical for SRF cavity protection in case of both accidental vacuum failures and planned maintenance. Initial results of the analysis are to be presented. We will discuss its potential use for predictive maintenance at SNS and perhaps similar SRF accelerators where cryomodules are interleaved with warm beamline sections.