Son-n-law's '99 Silverado (2000 bodystyle) has a refrigerant leak. Highside service port was leaking when I began this adventure so I replaced it. Pulled VAC for a couple of hours, let it sit for 20-30 minutes, appeared to hold vac so I charged with freon and sent him on his way, thinking I dun good. Thinking I dun good, stopped short when within a couple of weeks it was/is low again. Pulled plastic cowl off top of radiator support to see cond coil. No visuals of a leak(oily spots etc...) soaped coil, no bubbles. Soaped all connections and visually checked the compressor, no oily looking spots(and who decided to put an A/C compressor down there?!? dang, double dang). Service ports don't seem to leak as don't the accumulator/dryer. Soo,,,I guess I'm asking where is, or is there, a common leak place on these 1999/2000 year model trucks? And if it is the EVAP coil as I suspect, how hard is it to get to/replace it? Doesn't appear to be simple, hoping I'm wrong.