Mabye I think that the gurgling is normal because I ve been driving around with air in my heater core. I mean It dosent happen often, and just when the heat is on. But I do not experience any adverse effects like overheating or HG problems.

It is a bugger to fill my v6 up with coolant after I have drained it. I have a 3" body lift and that elevates the rear coolant lines and heater core higher than stock. I park it on a ditch incline and ilde it up with the heat on. The last year I put coolant in when changing my thermostat. It was only a half fill and it still took me a few hours to get her to accept coolant until she was full.

Anyway I hope that your problem is just an air bubble.