[Tony Van Helden]

My passenger side compressor required a shut down today and in search of an air leak, I located a strong hissing in the blumbing bay.  When I turned compressor on and off again, it took 27 seconds for hissing to stop.  Did a soap test and nothing noted on what I could see to get at.  What is behind or near there that I might be able to access to chase this one down or what might I be up against, figuratively or literally?
Thanks much!