I have a 2002 Century with the 3.1 engine. Last year i blew the head gasket, ripped it all apart and replaced all the gaskets, head, LIM/UIM, replaced the thermostat while i was there. A couple months ago, i started having an overheating problem, so I replaced the rad cap, then the water pump, then eventually the radiator cause it was rusted out. Still overheated. Next day, i blew the LIM gasket. I ripped it all apart again and replaced all the gaskets again. Now it'* back together and still overheating and i have no heat in the cabin, unless i rev the engine up, then the heat kicks on and the temp of the car comes back down to normal, as soon as i let go of the throttle, it overheats again and the heat goes away. Is it possible that the belt isn't tight enough, so that when i rev the engine and get the rpms up the flow is better and things work, or could it be that the stat i put in last year is gummed up. i can tell ya, when i open the bleeder screw on the stat housing, i get air and steam, then i hit the throttle and wait a sec and i get coolant out.

No heat in the cabin and engine overheating ... sounds like air in the system.

theres two bleeder screws on that engine one on that metal bar by the pass side and one by the throttle body if its like my 3400 was