The Freon line to the central heat and air unit for the second floor unit run across the ceiling of my bedroom. Recently just before the air handler starts I hear a spewing, or gurgling [ like rushing water] sound. The unit appears to heat/cool OK. Is this something I should be concerned about?
The outside unit is at the basement wall, about 30 feet vertical and 50 feet horizontal from the 2nd floor air handling unit.

AMHD has some very good people, plumbing, electrical, computers, etc. When it comes to dogs, I am one of them. When it comes to HVAC, a few other and I are doing what we can, but this is one I don't know. It sounds like something is wrong. Even if the system continues to run, it may not be as efficient as it should be. I can't say if you have a problem with the expansion valve. I can say, if it has a problem, you will have to have a technician fix it. All this leading up to a lame, call a professional. Sorry.

By the sounds of it you have a hydro air system in your home this being the case and not knowing your location ill assume you are in heating mode the rushing/gurgling sound you are hearing prior to your unit starting up is air in your water lines going to your coil without going into great detail because I may be wrong about the hydro system but if I am correct this problem can be easily corrected by bleeding the heat loops... if I am correct about this being a hydro air system please let me know and ill provide further instructions on how to bleed it if necessary if it is not a hydro system let me know and ill provide the a/c explanation for the noise you are hearing... please let me know either way... thanx

Sorry for not being more detailed. The system is not hydro air. It is conventional Freon heat/cooling system [heat Pump?] . I live in central Alabama and the sound began during this heating season. I have not used the cooling side this season as of yet. Not sure if it makes the same sound or not. A friend seemd to think that the vertical Freon lift of roughly 30 ft from the condenser could be the problem. The unit is only three years old. I appreciate any advice you might have.