Check gauge light - 1994 Chevrolet 1500

[George_San_Jose1]

The gurgling is most likely caused by air trapped in the cooling system. As the air bubbles go through the heater, tends to make a that sound and is usually quite audible in the passenger compartment. Normally a cooling system doesn’t lose more than one or two cup of coolant every 6 months. Since you are losing much more than that, best to tow the vehicle to a shop and let them do the diagnosis. When you turned the heater to “off” it probably eliminated the coolant flow through the heater core, so even though it was low on coolant, more coolant was left to cool the engine. You are right, usually when turning on the heater and fan to max heat, that will cool the engine a little. But it only works if there is plenty of coolant remaining in the system. Best of luck.