Hissing noise coming from the rear of the car. I

It is a vacuum line, replace it.

Depends on the noise. Tapping or knocking is rod bearings, engine side. Whining is the transmission side. Torque converter, pump, and parts further inside the transmission.

Pipe is out side on passenger side,under behind wheel,could be dirty or close.Try to move or open.

loose hose clamps hole in one of the vac lines it seems to only hiss when its under pressure

This noise is likely the expansion valve making noise.

Just a suspicion: hissing noise comes from failed/jammed/malfunctioning motor to move the door
in the ducting to route heated air to the hoses/ports for "heater" and "defrost."
Problem: failure of motor/linkage to heater/defrost selector door under the dash on the passenger side.
Also sounds like you have not blown fuse to this selector door.
Also - hissing noise could be air being forced against the closed door (which should be open) - in this
case, you'd want to check the fuse to the heater/defroster actuator door.
The rear heater works since its function is not related to the operation of the front heater/defroster.

inspect the braking system for warped or uneven rotor surface, as this may cause this noise and uneven pad wear. CV joints also could cause this if the boots are torn, have insufficient grease, are damaged,or have worn bearings. Hopefully this helps

did you just get the compressor replaced?
if you did or got it recharged i think its normal to hear that.

like grinding sound ??
if so it's your wheel bearing.

yes that is the expansion valve! there is a hissing sound from the restriction in it for a pressure drop thats what makes the a/c cold the hissing is normal