high, low, and oil levels are measured to manufacturer specification. the metal-to-metal is at the compressor, and the hissing is coming from where the fan/evaporator is. the hose that goes into the unit is pressurized, but the other sides hoses are completely flat.

 so I will again check the clutch. is it usually electronically actuated? the system I have is from a company called ProAir (my truck didn't come with an AC so I put it in because it's a spare out of an old work van I had) and