Chevrolet Repair: Pick Up, coolant levels, coolant fluid

Question
I have a 1999 Chevy 4x4 Silverado 5.3 liter.  It makes a gurgling sound from under the dash, near the glove box.  Any ideas?  Thanks Ryan.

Answer
coolant fluid, heater core, probably low coolant levels or the air is just running, the a/c i mean. anyhow are ya leaking? if yes then check to see if you can find said leak and stop it. if no leaks then check all fluid levels possible.  hope this helps