Your coolant is low.
Low coolant and air in the heater core.
The gurgling sound is caused by pressure in the engine coolant system(antifreeze) slowly releasing into the coolant overflow resevoir. Typically a faulty thermostat causes this sound.
The noise you hear when drinking from your Hydro Flask is likely caused by the air pressure inside the bottle equalizing with the outside air as you drink. This can create a popping or gurgling sound.
That is where the heater core on most automobiles is located - just inside the passenger side dash. When you turn on the car's heater, water from the radiator is passed through the core under the dash, heating the air that comes out the vents. It's perfectly normal on some less-expensive vehicles to be able to hear that "gurgling" due to lack of noise reduction material in the cabin. However, it can sometimes be a sign of overheating due to running low on radiator fluid or a faulty thermostat. Check the fluid levels in the vehicle and have the thermostat system checked.
When you first plug in the heater have the hood open and in a few seconds you should be able to hear the heater kicking in. It will make a sizzling noise.
You have air in the system that has to be bled out
I had this happen on my 2001 S-10. I had a very slow coolant leak and when the coolant would get low I could hear what sounded like water flowing from around the heater. At first I thought I had water built up inside the A/C evaporator which was gurgling, but finally realized it was a coolant problem. Once I fixed my leak and topped off the coolant the noise was gone. Hope this helps.
yes, the fan bearing is worn out
"Did you hear that noise?" -or- "Did you not hear that noise I just heard?"
Easiest is to plug in the block heater cord with the hood open. Follow the cord to where the block heater is located and you should hear a gurgling sound similar to an electric kettle. If you don't check your power source. If you can reach the block heater unplug the cord from it and check the power at the end that plugs into the heater with a 2 prong tester to make sure it's not the cord causing the problem.
Easiest is to plug in the block heater cord with the hood open. Follow the cord to where the block heater is located and you should hear a gurgling sound similar to an electric kettle. If you don't check your power source. If you can reach the block heater unplug the cord from it and check the power at the end that plugs into the heater with a 2 prong tester to make sure it's not the cord causing the problem.
If you hear gurgling pipes in your home, it could be a sign of air trapped in the pipes or a blockage. To address this issue, you should first try to identify the source of the gurgling sound. If you are unable to locate the source or if the problem persists, it is recommended to contact a professional plumber to inspect and fix the issue. Ignoring gurgling pipes could lead to more serious plumbing problems in the future.