Overheating

Car doesn't show typical blown head gasket symptoms ie: oil looks clean, not watery or milky, no smoke in tailpipe, no water at tailpipe, runs strong, not missing, head could be blown between cylinders I guess and not shown signs yet. I have now taken the thermostat out and car seemed to get real hot even faster. I see that these 3100 engines are notorious for blowing intake manifold gaskets...anyway, water seems to get hot (boiling) and just blows right out overflow reservoir, then temp gauge inside the car of course pegs out and temp light comes on, at that point, if I open bleeders, nothing but steam or just hot air...

Thanks Jim...I will definately try the pressure tester...

I have a 2006 Century and about every 8 weeks it starts running hot, "burping" it has fixed it every time so far. By burping it I mean when it runs hot I loosen the radiator cap just a very small amount, just enough to let the pressure off but not enough for steam or water to come out. When the water in the reservoir quits bubbling, I tighten the cap back and it seems fine. Sometimes it takes a couple of times to fix. I think air pockets get in the system and doesn't let the water circulate like it should.

Lower intake manifold gaskets are definitely a very common problem with the 3.1, 3.3 L engines. It's not a matter of if, it's a matter of when it will go. Oil will often go into the coolant. If coolant gets into the oil, you have a mess, maybe a junk motor. If oil gets into the coolant, get the L.I.M. gaskets changed immediately and flush the coolant system thoroughly. Don't let it go because the cooling system will deteriorate and this can only cause more problems and/or engine failure.

I forgot to mention in previous comment, make sure to check the heads/head gaskets and repair/replace them too or you'll end up doing the L.I. M. gasket change for nothing.