Nissan Repair: Maxima overheating, radiator cap, nissan dealer

Question
I have a 2000 Maxima that I cannot figure out why it is overheating. It was fine all winter but as soon as it got hot and I turned the A/C on it started to climb to peg out the needle. I flushed the radiator,changed the thermostat,changed the thermstat in the water valve,checked the oil for water in it came back clean with no antifreeze or contaminates in it but it still overheats as soon as I start to drive. It does not overheat idling in the driveway even with the A/C on. A/c blows cold air and heat is hot. Took it to the Nissan dealer who said the water pump was ok. I do not know what else to do. Please help!

Answer
Brad,

Check to see if the fan comes on when the airconditioner is off.  If the fans come on when the air is on then the relay is bad.  If the primary fan does not come on then it is the primary fan that is defective.  I would check these first.  Also, change the radiator cap for a factory one to make sur the pressure is good to keep it from overheating.  Now, if the headgaskets are good and the above does not work then the timing is going to have to be retarded via the consult II if it is pinging and that is causing the overheating or you could use premium if you are not.