Previousl I would use half a can of R134a and it held for 12 months. Now in 20 hours the leak evacuates my system. I watched all Scotty's videos on AC. I borrowed gauge and vac from Autozone. The system had zero refrigerant as it leaked out. I changed 2 orings on the HP and LP lines that attach directly to compressor as many Subaru owners say these orings are cheap and often fail. After the new orings for $2.05 I hooked up gauges and vac. I got the system to negative 29 and let it run for 30 minutes. Then closed the valves and observed if the system held pressure. After 15 minutes it increased to negative 25, then negative 20 and after about 25 minutes to negative 15. So to me the orings were not the problem or there is multiple leaks. What I noticed was when I removed the low pressure hose a "swoosh" of air rushed into the line through the LP valve. I quickly put my finger over it and I could feel suction quite strong. I released my finger and air rushed in again. So I bought a valve core tool and tighten down the valve core but the generic cores do not fit my vehicle.
My question is does the fact air rushed in to the LP valve PROVE THAT IS THE SOURCE OF THE LEAK WHERE THE SYSTEM IS COMPROMISED TO HOLD VACCUM?
Well, replaced the schrader valve core in the lines and problem solved. The low pressure valve core had a very loose spring. Cold AIR, holding pressure!! Yippy
That could well be, the Schrader valves can definitely develop leaks. (You didn't say how old the car is.) If you use some ultraviolet dye or an electronic detector that will let you know for sure, but the Schraders should be cheap and easy to replace. Make sure you use valves rated for refrigerant and not tire valves.
2014 with 115k miles. So I popped out the Schrader valves. Subaru told me both High and Low Pressure lines used the exact same valve cores. The Low Pressure valve has a very loose spring. The High pressure one has a lot of spring still. The Low pressure spring is very unresponsive. My guess is this is the faulty seal. I plan to buy a new one Monday and replace it. My guess is the suction was stronger than the weak spring and caused a weak spot. I replaced 2 orings and this valve will be replaced come Monday. I will follow up. Thanks
Any input is greatly appreciated. Thank you.