1999 Chev Tahoe 150,000

I recently replaced the intake gasket for the second time. Since then there has been a water noise or gurgling sound coming from the dash area. It is not an air pocket I burped the system. Cannot tell if it is the A/C or Coolant. The sound it is making sounds like coolant but the mechanic that replaced the intake gasket blocked off the heater core and it still making the noise. Noise started the day the intake gasket was replaced. Changed tentioner pulley, replaced water pump, drained system and refilled it again. Could it be the gasket that was installed wrong? If A/C what could it be? Any help or suggestions would be greatly appreciated.