AC Accumulator Hisses After Turn Off Engine

[wildcatgoal]

The AC accumulator doo-dad on the passenger-side firewall of my 2002 Tahoe (it's covered in a silver thermal blanket) makes a loud hissing sound when the engine is turned off. The sound trails off after it seems to "lose pressure". Has anyone experienced this? Is this normal or am I about to find out how expensive it is to repair my AC system?

 

[wjburken]

@UmmScott

 

[OR VietVet]

It is normal. Based off what you posted. If the system is working as it should, blowing cold air, it is the sound of the pressures equalizing in the system at the orifice tube. When working your pressures can be 150 psi or more difference. When shut off the system equalizes. It has been doing that all along but you just may not have heard it or paid attention before. If is louder than normal then the orifice may be partially blocked with debris. Use the system for now but may need a/c work later if it gets blocked all the way.

 

[wildcatgoal]

Okay, thanks! The AC seems to be working. I haven't really needed it to COOL DOWN vs. just condition the air without much temp difference between inside/outside yet this year, so we'll see.

 

[OR VietVet]

If it does clog the likely source of debris is from the condenser as they break down from the inside. Also from inside the compressor. If a compressor needs replaced and you open an a/c system and start replacing parts, you will see debris in the orifice, which is normal after so much time and pressure works on the inside of the system. You always replace the compressor and the orifice and the accumulator. You would also always flush out the open system. IMO, the condenser should be replaced as well. Small passages in there break down and get clogged and make a big difference when it comes time for the condenser to dissipate the heat that is sent to it. If old enough I would change out the hoses as well because they get debris embedded in the inner linings of the hoses. Thankfully, the evaporator is stouter and can take some crap before it needs replaced.