Hissing/ air release sound has been asked about before without a definitive answer even when people had in for service, well last night I spent some quaility time with my Pony and found out what that noise was.
on mine at least (for sure) it is just the A/C compressor clutch engaging and disengaging, in a very quite (1AM) enviroment I was under the hood adjusting head lights when car was runing w/ A/C on and PISSST the clutch disengaged, looked with flash light and confirmed (compressor is on lower right of engine)
inside the car when this happens (more if your windows are down and sound bounces of a high curb like when crusing the strip) it does sound like a release of hi pressure air but up close to compressor it is just a metalic sound
this is one less thing we have to worry about, hope this helps
on mine at least (for sure) it is just the A/C compressor clutch engaging and disengaging, in a very quite (1AM) enviroment I was under the hood adjusting head lights when car was runing w/ A/C on and PISSST the clutch disengaged, looked with flash light and confirmed (compressor is on lower right of engine)
inside the car when this happens (more if your windows are down and sound bounces of a high curb like when crusing the strip) it does sound like a release of hi pressure air but up close to compressor it is just a metalic sound
this is one less thing we have to worry about, hope this helps