I take it that by "air lock" you mean a bubble in the line? I know when I did the t-stat on my Jeep, once I got it back in and the housing back on, made sure all my hoses were connected and started refilling it with coolant. I filled it until it was full, worked the radiator hose until the fluid went down, filled again, and repeated this process until the fluid level didn't drop anymore. Then I left the radiator cap off, started the engine, let the fluid level drop and just kept adding coolant until it was topped off and there were no more air bubbles in the line. Are you leaking anywhere or just running hot?