1997 Buick Century Cooling system

I am having problems filling the cooling system. I can't seem to bleed all of the air out. I found a bleeder on top of the engine where the radiator hose attaches to the engine and then on on the front side of the engine on the heater hose. I have opened both of them up and added coolant directly to the radiator but it still seems like I need to do more because the temperature guage has large swings and the heater sometimes work. Hope you can help. Thank you, Doug