Cadillac Repair: overheating, bolt holes, head gaskets

Question
I have a 1994 Seville that overheats. I have changed the water pump, the radiator and the thermostat. I even tried running it without the thermostat, but it still runs hot. It also seems to lose antifreeze, but there are no external leaks. It doesnt blow white smoke. The fans both come on, but dont seem to do anything as far as cooling it down. Sometimes it stays at 199-200 and then it will jump to 235-250 and then back down. Its wierd. It doesnt have any antifreeze in the oil, or any oil in the anti freeze. To me it seems like there might be air in there because I can only get it to take two gallons of coolant max and I know the system takes more than that. Any ideas? Thank you

Answer
What you have is a classic example of a faulty head gasket allowing combustion chamber pressure into the cooling system. This IS very common and you will need to replce the head gaskets and heli-coil ALL the head bolt holes and install all new head bolts per factory recommendations.