Rep Power: 0

I turned my AC on and there was a pretty loud leak noise so I turned the AC off and the noise stopped. Each time I turned it on there was the leak until I turned it off. There is now no sound and there is no pressure left in the low pressure side (when I press the valve there is no sound).

Is this enough information to narrow down where the problem is?

Thanks for the help.

 
Rep Power: 223

Sounds like you have a pretty large leak in the AC system, start looking around for evidence. If it was loud enough for you to hear it with the engine running it should be pretty easy to find

 
Rep Power: 0

Does the fact that it only occurs when the AC is on, indicate any place in particular...
like shouldn't it be after the compressor for example?

 
Rep Power: 120

Hissing sound heard in cabin is common when the system is low on pressure, an actual leak that you could hear would deplete the system in less than a hour.

My guess is your system has had a slow leak and once the level got low enough the expansion valve started to emit a hiss type sound as vapor arrived to it instead of liquid.

Might be a pinhole leak somewhere, or as simple and likely as failed orings.

 
Rep Power: 0

@Slumpertcivic Thanks for the advice!

I see that this guy injects some refigerant into the system and hears the same hiss.

He thinks it's a leak at the expansion valve but doesn't find the leak there with the dye. This sounds a lot like what you are talking about. He is probably just hearing the hissing of the gas pass the valve.

Is the easiest way forward the following?
1. Replace the easy to reach o-rings.
2. Vacuum out the air to remove moisture (Is this absolutely necessary if I live in a dry climate?)
3. Refill with hcf134a after adding a bit of UV dye to the low pressure hose.
4. Hope there is no longer a leak.

 
Rep Power: 225

First step should be to check the pressure in the system. I think you can rent a set of gauges at Autozone/others, or take it to a shop and have them troubleshoot.

If the system is completely empty then it has to be vacuumed before filling, the air dryer should also then be replaced.

 
Rep Power: 0

Nothing comes out when I press the low pressure valve. Doesn't that mean the whole system is empty?

I unfortunately don't have the option of renting tools anymore because I moved to France .
I'm trying to evaluate the cost of this repair. I would have to buy a vacuum pump and gauges for around 100 bucks.

 
Rep Power: 225

I missed that part, yes the system is empty. I'm not sure how much a shop would charge to troubleshoot but if you have a pump and gauges it's not difficult to fill yourself. First you'll vacuum for 30-45 minutes then check back after a few hours to see if the vacuum has leaked. If it has you'll have to find the leak before filling.