gurgling noise in dash

except when I turn a sharp right or left I can hear a gurgling noise in my dashboard. I think this is my heater core but I'm not sure. I've checked all the fluids (oil, transmission, radiator, power steering) but everything is full and have found no leaks underneath. My heater still works but I have noticed in the past couple of days that the temperature gauge doesn't go up as high as before.

It sounds like you have air in the cooling system, quite possbly from a leak. I would be looking for that seriously. The temperature gauge can read LOWER when there is air at the sensor rather than coolant and damage can be occuring.

except when I turn a sharp right or left I can hear a gurgling noise in my dashboard. I think this is my heater core but I'm not sure. I've checked all the fluids (oil, transmission, radiator, power steering) but everything is full and have found no leaks underneath. My heater still works but I have noticed in the past couple of days that the temperature gauge doesn't go up as high as before.

Check the drain tube that comes through the firewall behind the heater core. Sometimes they clog. If it is you can rod it out with a piece of stiff wire. BTDT.

I presume the coolant overfull tank is what you looked at to check the coolant level. I wonder if it's possible for a bad radiator cap to allow air into the system while still displaying coolant in the overflow tank. Or a hole in the hose which goes to the overflow tank, preventing the transfer of coolant to and from the radiator. Or both. The radiator cap would be just something to check (or maybe just replace anyway as periodic maintenance, they're only a few bucks). I'd think if you had actual coolant sloshing around in the heater box you'd smell it and have foggy windows, etc.

I just changed the water pump on my 99 jimmy, I heard that gurgling sound when I first started the truck back up, it happened when I revved the engine a bit, that to me was the sound of fresh GREEN antifreeze traveling to the heater core.

I had that noise in my 96 Jimmy, and I think it was air. I had a leak in the radiator where the oil cooler line connects at the top. The radiator would drain to just below that level, and you'd hear the gurgling. I fixed the leak, replaced the thermostat and radiator cap, and refilled the system, problem solved.

Do you have AC ? Often times the evaporator makes noise when refrigerant stops circulating. Nature of the beast. I agree with the other poster that it could be air bubbles in heater, or clogged cowl drain.