I have a 2003 ss Monte Carlo I've change the thermostat I've changed the radiator I check the coolant and it still runs hot with the temperature gauge have something to do with it?Or water pump?

also, when hot check the lower rad.hose to make sure it is not closing/collapsing ...how hot is it running in stop and go/steady cruse?

Do you feel as if it's over heating or are you just going by the temperature gauge. You may just have a bad sensor from engine block to temperature gauge giving you a false reading.

Firebird338 that was my first guess also. A twelve year old car is just about when the sensors go bad. If Steve can't tell by smell or sound that the car is over heating, than it just may be a bad reading on the gauge. If that was the issue, of a bad sensor, who told this person to spend all that money to put in a thermostat and radiator? Too bad he didn't ask here first, but then we don't know the condition of the radiator and if the thermostat was bad either. Kelly is correct in telling him to check 12 year old hoses. Mechanical things do wear down and go bad over time.