Chevrolet Repair: 1996 Chev Lumina, chev lumina, losing coolant

Question
My car keeps running hot. The mechanic has changed relay switches, thermostat, catalytic converter, fixed radiator, fan motors, & a couple other things. The car is still running hot. Please help

Answer
Are the fans coming on?  is the car running hot or is the gauge just say its hot?  The gauge in the car might be off.  I have seen the coolant temp sensors read wrong on these cars, as well as the main problems....which are head gaskets and intake gaskets.  If you are losing coolant(can actually see the leak) chances are its the intake gaskets, but if you are losing coolant and can't see the leak it's most likely a head gasket.
Jimmy