Ac noise 2006 Honda pilot

More than likely this noise isn't an issue. What you're hearing is the system equalizing through the system. In order for A/C to work, there has to be high pressure refrigerant which gets cooled, then it goes through an expansion valve as it enters the low side. This allows the refrigerant to cool, which then goes through the evaporator where the interior air flows over it and is cooled for your comfort. Without the pressure differential, your A/C will not work and there wouldn't be a noise, either.

I'm not saying there isn't a leak, I'm just suggesting if you've put refrigerant in and it's cooling now, the noise you're hearing is most likely the system equalizing. If the noise you are hearing was prominent enough for you to hear it, your system wouldn't stay charged for long and you wouldn't get the cooling benefit but only for a little bit (as the refrigerant would have all leaked out).

That could possibly be a leak.

One way to find out is to wait several hours and test again - if it has stopped working then there must be a leak... Also if the hissing as stopped.

Getting someone to put gauges on it and seeing if the readings drop will probably be quicker.