2002 2.2L cavalier over heats. found a radiator leak, replaced radiator and t stat. 6 mo ago I replaced leaking water pump. bottom or the radiator stays cold while the top seems a little warm. there does not seem to be much flow, System blows heat until it overheats. I have bled the system. Still can not seem to get anywhere, I have to keep adding a little coolant. No white smoke through the exhaust. Bobbling into the overflow tank comes and goes. Poss head gasket but the eng runs to good.

Any one have any suggestions ?