ok,
i had no problems for the most part until i had to go out of town for a couple months. my car was only driven a few times while i was away and i do not think any the last month out of the three. anyway, i have a 2005 g35 coupe and now it runs like normal and at normal temp (whether ac is on or not) for probably 20 minutes give or take. it stays at the normal temp on the gauge during this time, then finally starts getting hotter it seems in small increments until it shoots to the top. also, if i start even hours later it gets hot quick, but if it sits overnight or for quite a number of hours it will do as stated above. i have checked fluids, nothing is leaking (water pump, radiator, etc), and everything seems fine. i could be mistaken but i sometimes think i am smelling antifreeze when i get out of the car, but it could be some i have spilled when adding. anyway, i bought a system flush kit with the tee you put in the heater hose and will try that sometime today. any help with this matter is greatly appreciated. thanks,
brad

 

have you checked the thermostat?

 

Are you getting any leaks?

How many miles on your car? Have you flushed the coolant?

I doubt the T-Stat is your problem - it would happen sooner and much faster.

Possibly a pump going bad??

 

i have actually changed the thermostat already. i forgot to mention that. i have tried checking the fans, and i'm not sure when they are supposed to turn on, but i have noticed they do both come on at some points. i am going to try flushing my coolant today. my car has right over 100,000

 

did you test the thermostat to make sure it was working before you installed it?
-Drop it in a pot of water and heat it up. Should open before it boils ~170* or 180* depending on which thermostat you used.

If you changed the T-stat already you might have an air bubble still stuck in the coolant system. Not that likely considering your erratic heating problems. Maybe the water pump is going bad?

 

I am having the same exact problem in my 2004.

Changed the lower themostat and did not solve the problem. Is there a second thermostat like there are in other Nissans?

 

+1 I just got my free fan installed at the dealer on my '04. Now it idles below normal temp in 100 degree weather.

 

only 1 thermostat

 

In my testing, after starting a cold engine both fans will turn on moments after turning on the AC.

 

I'm a "Z" guy who was bored and saw this thread and thought I'd throw something out there. The VQ is notoriously picky about air in the system. Being you've change the T-stat already I'm assuming there's air in the system. Bad News, the VQ is also really tough to get all the air out of the system. I'd say keep bleeding the system. A quick check of the cooling reservoir (but not a definite source) may confirm it. If it is dry you know the problem is air. The water pumps don't really go bad in these engines, and if you can go for 10+ minutes the T-stat is at least working (could still be a problem but not likely). Also note if the car is only overheating when you stopped or in traffic consider double-checking the fans.

 

yeah, i was told by firestone today that it's the fans. they do come on, but they turn off here and there and i can tap them or mess with the connections and they turn back on. i am going to try to clean the connections with electrical parts cleaner today and worst case replace the motors. i just don't see how both fan motors could be faulty especially since they both do come on at certain times.