My pontiac keeps over heating we have changed the upper an lower hoses the radiator the thermostat and water pump and raditor cap why is it still over heating

Is the water hard in your area? If so, you might have to have your radiator "rodded" out. I live in south Georgia and there's a fair amount of lime in our water. I have to have my radiator rodded out every 4-5 years.

Mark they changed the radiator already. If you have already done what tom said. There is a kit that tests for head and head gasket leaks. http://carquest.com/webapp/ wcs/stores/servlet/ product_CARQUEST+Specialty+Tool s+by+Lisle+Combustion+Leak+Dete ctor+Kit+- +Quickly+checks+combustion+leaks +which+are+in+the+cooling+syste__ 10151_-1_10651_627435_? acesApp=0 ........delete the spaces in the link. It is very simple to use, it runs off engine vacuum.

mine did that too, it was the head gasket, my my neighbor mechanic it costs $500, the parts alone is around $200, the cost at a garage is much more.

I would bet any money your intake gasket is shot. Very common on these cars.

If its the intake gasket then the oil will be full of coolant

Not in every case. Most commonly yes. But the intake gaskets can leak externally or could send coolant down the intake ports to be burnt out or if bad enough hydrolock the motor. Have experience all 3 cases personally.