Hello all, I have an a.c leak. It usually takes about 2-3 weeks for all the refrigerant to leak out and start blowing warm air. I have used stop leak with no luck. I want to use some dye and a uv light, but dont have the extra money for the light right now. My question is , after charging the system, and getting ice cold air..... I shut the engine off, and I hear a hissing sound which lasts for about 30 - 45 seconds. It seems like its coming from the dryer area, but when I spray soapy water around all the fittings ,I get no bubbles? The sound is like air escaping...... Is that a normal sound to hear after shutting down, or could this be the source or the leak somehow? Thanks for your help Bill

 

You will have a terrible time getting anyone to repair the system after you put sealant in it.

A hissing noise is common.
For a proper repair the system must be evacuated and repair whatever is leaking.

Not one person will jeopardize their recovery machines when they discover sealant.

 

If it's the 99 in your sig, it has dye in the system from the factory.
You can use a cheap UV light from Auto Zone, but you need it in the garage out of full daylight. It also helps to shade the engine compartment. The available yellow glasses help a lot with the UV light.

Pay close attention to the compressor body and even remove the clutch plate to check the shaft seal.
Look for signs of oil/dirt around all of the fittings and crimped hose connections. Dirt/oil usually means a leak.

Regardless of where the leak is, you should flush the sealer out of the system and replace the accumulator and orifice tube.

 

The hissing sound when you shut down is just the freon equalizing pressures in the system.