Unless the engine is overheating, you have air trapped in the system. Park the car on an incline or jack up the front as far as possible. When engine is cold, remove the radiator cap, set heater controls to hot, and start the engine. Make sure the radiator is full and watch for air escaping. Keep the coolant level full and when you see not more air bubbles escaping, you are done. Replace the radiator cap, and see if the sound goes away. If not, take it to a professional.
The coolant level is low in the truck.
The heater blower for a 2002 Chevy Silverado is mounted under the dash. It is on the passenger side, in the heater housing.
The heater inlet hose is on the firewall. On the 2002 Silverado it is close to the bottom of the firewall on the passenger side.
10000.00
If it is a gas engine, then no. If its not gas then yes.
Overheating. Have the cooling system checked.
Check your coolant. Is it thick and gunky?
Nope.
maybe the heater core.
Your heater relay switch may be bad
you now get over it
Broken line at the heater core possibly