My 2004 Suburban 2WD LT with 105k has a noise from behind the dash when the car is running and everything else is off, including AC. Itt sounds like fluid bubbling in a hose or plastic gears turning. The car runs fine, it is just an annoying noise that I would like to fix before it becomes something worse.

Any ideas?

 

My guess is there is air in the cooling system and you are hearing the bubbles purge themselves to the highest point in the system once the fluid has stopped flowing.....
Check your anti-freeze level and or consider having the system flushed...

 

Coolant level is fine. It has been rock solid since the water pump was replaced and coolant was flushed a year ago.

 

I suspect it is just air in the cooling system and its probably been doing for some time but just never heard....you were probably in the the vehicle for a few moments longer then normal so you got to hear it....
But we will see what others have to say... it what the forum is all about

It could also be vacuum releasing from actuators but most newer vehicles have motor driven vent actuators then vacuum driven....