My Z totally Doesn't do well in traffic.
 

A little after I got my 2005 350z Touring, I noticed it had an overheating problem. When im in traffic and the car is imobile, the gauge starts to creep up and overheats until im riding freely. I did alot of searching on this website and it handpicked a bad thermostat being the problem for the Z's overheating. Today I went in and had the thermostat changed and on top of that I had them give my Z a full service. After the Z was done, I took it for a ride and encountered traffic and slowly but surely the needle started to creep up borderlining the overheating marker, then began to very slowly go back down when i got out of traffic and turned the A/C off. This is my first nissan, not tom mention its my first sports car. Is this how it should behave in traffic or when imobile or is there something else that is causing my Z to overheat when its on but not moving. Real Help Needed.Thanks.

If its overheating while stopped but its fine while running its probably your fan, the exact same thing happened to be about 3 weeks ago. Car would overheat while stopped at a red light or with slow traffic but temp would drop down to normal if the car was running. Get your fans checked.. I had to replace mine, 600 for both fans + labor, thankfully i had warranty so i paid $0

In 4 years have never had a heating problem and we frequently get up to 105 in the summer.

The old thermostat that was replaced did you test it to see if it opens and closes?

Im not sure how to check for that. I still have it with me. It looks pretty beaten up so I think it was dued for a change aswell.

I would definitely check if both fans are in working order.

COuld there possibly be something wrong with the radiator? Just a Question. I think ur Right Bcuz I don't ever remember hearing the fans kick in.

Sounds like air bubble still in the system. Try bleeding the cooling system using the instructions at the bottom of this page...

http://crackaddict.com/~flynn/howtos...amco.howto.htm

Put it in a pan of water on the stove. If you are really sharp you can add a thermometer. But the thermometer is not a necessity. Just as long as it opens and closes.

Surprised that the mechanic who installed the thermostat did not do this.

Defintely a break down in the cooling system. My car has gone through uphill on the grapevine for 45 mins in 100 degree weather and its fine (with A/C on btw). I'd check if there is air bubbles. Also is the fan working and goes on when the A/C is on.

Most people and mechanics would just fill it with water, run the engine for a few minutes and assume that the bubbles and air pockets got filled and leave it at that. As we have seen over the years, that's not good enough. The FI guys see this problem all the time, car runs fine until they stop. At idle, there's not enough flow through the system when there are air pockets present.

Whats the probability that its the fan and not the air bubbles vice versa. Both diagnosis sounds solid. I think i'll have to go with teh cheaper one first so i wont waste any money gettin unecessary work done.

... Try and listen for the fans.... when/if they kick on and then see if the temp drops.... it doesn't sound like air pockets in the system b/c you said it goes back down when your driving. If it does go down when your driving religiously..... then it has to do with air going through the radiator.... start from there....as said before, the fans etc....

If not air pockets, consider the possibility of the fan clutch being defective? Check to see if it's bad (turn the car off, if the fan still spins--the fan clutch is bad).

There are half a dozen potential reasons for cooling system troubles.

Not certain if the mechanic who replaced the thermostat checked for the obvious. Instead of guessing and throwing your money away, why not have a competent mechanic diagnose the problem?

Did we get a resolution?

OP did you figure anything out?

I think if the radiator was the issue it would overheat all the time, not just while stopped. I would get the fans checked. As well as following some of the advices from the previous posts.

I had a similar problem with a jeep. Cruising was fine but would overheat at stoplights/traffic. I replaced the thermostat and water pump before I found out the serpantine belt (which drove the water pump) was worn. Replaced the belt and ran like new. A worn belt will slip and won't spin the water pump fast enough unless the rpms are up. I've never had this problem in my z, but its something to consider.

Edit: Also if the belt is fine but too loose, it will also slip. How many miles on your belt?

Here is what i did today. I started up the car, turned the A/C on and went to see if the fans where working. Only the fan on the passenger's side seems to be on. I purposely went for a drive so the car can heat up then parked on one spot with the A/C blasting. I opened the hood and only the passsenger's side fan is still the only one on. At this point the car is near overheating. Im guessing that, that is the problem right there? Arent they both supposed to be on at some point. The fan on the right never at once came on or kicked in.