99 buick centry overheating

a couple of weeks ago i filled coolant resevoir,it was low then started noticing that it was running hot. i opened radiator cap, turn engine on then let excess water run out .seem to be fine after that then when ever i started the car in the mornings to go to work within first 30 to 45 seconds the valves would rattle badly then stop and run perfect (oil level was full) so i ask around frinds thougt subpump was clogged no pressure to push oil up in engine until go warm. suggest use duralube. so i changed oil 10w 40 and duralube found small amount of froth in oil after that went to store whenhalf way there temp gauge when to h fast. i changed thermostat same thing happen temp gauge went to h both time never smoking felt like coolant was not going into engine and the problem with the rattling is still there. talked to several people,they dont know whats wrong,thought it might be head gasket but dont know, i read that the intake manifol gasket is a common cause but dont know,also when the temp is real high the temp light doesnt even come on.

First- Use 10W-30 next time

Second- Are you using DEX-COOL coolant? It's orange. The green stuff is not supposed to be used in these cars.

Head gasket maybe? does your oil level rise at all?

thank u for replying i went to dealer they said it was the intake manifold gasket,i replaced that but it is taking me several days to put it back together so i'm trying to find pictures of that motor size but no luck if any one knows where i can get some on the net please email me at robh6287@yahoo.com
thanks