The ac compressor was replaced and ii noticed a hissing sound like air escaping in the front of the car as soon as I turned it on and while idiling
My car has 170000 miles.
My car has an automatic transmission.
It sounds like the AC lines may still have a leak in them as indicated by the hissing sound you describe. This is a common sound when there is a leak in the AC system. As the AC compressor builds pressure and compounds the refrigerant, this creates a very high pressure system. When there is a leak in the system, this will produce a hissing sound much like you describe. I would suggest having a professional from YourMechanic come to your location to diagnose and inspect your vehicle.
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