Why does the Antifreeze run out of my 2003 Buick rendezvuos when i remove the radiator cap to check the antifreeze Level

If its while its running either exhaust in coolant from yet another head gasket problem or hot and has to go somewhere.

On may newer cars, the radiator will be full up to the cap, If you open it when it is anything but cold, you may get some running out. If the coolant is at the top of the filler you are fine, Then check the coolant resevoir and make certain it is to the full line.