Nissan Repair: 98 Maxima overheating only when idling, temperature gauge, petcock

Question
So, as stated above, the car when either sitting in Park, or simply stopped at a stop light will begin to heat up. It will reach the danger zone on the temperature gauge. As soon as we start to drive for 10+ seconds it slowly drops back down to normal and safe temperature readings. Unlike others who have written that turning on their A/C will cause the fans to kick on and reverse the over-heating, turning on my A/C does nothing of the sort.  Only driving at speed of 35+ mph seems to do the trick and get the engine cooled down to normal.

Any ideas as to the most likely culprit? Should we be looking at the thermostat? Is it likely to also be the fan relay, even though the A/C doesn't trigger the cool down? Possibly radiator blockage and a good flush needed?

Your advice is sincerely appreciated. Thank you!

Answer
Hi Scott -

If the fans are working properly, then I would check the radiator. Unscrew the petcock that drains the coolant under the radiator and see if the coolant flows freely.

If not, then I would flush out the radiator. Also ensure that the radiator fins are not corroded and blocked by leaves, debris, etc.

Hope this helps -
aloha
calvin