Z near overheating. What's the issue?
 

Ok so just went for a 10 minutes drive here in PA where it is semi-chilly out today. The whole drive was stopping and going non stop. My dash temp gauge was very close to the high line and my a-pillar water temp gauge was reading around 240 degrees F which is very high (normally around 200). Ive never had overheating issues with my car so I figured it was the stopping and going.
I just went out and went for another drive without any stopping and going. The temperature climbed right back up to that point once I started moving.
At idle the temp gauge stays around 230 but as soon as I move it climbs.
At first I thought it was the fans not turning on, however I did check and the fans were running. My only next thought would be the thermostat?
Can anybody confirm or deny if the thermostat is the source?

thermostat or radiator cap (often overlooked), i would look at

Radiator cap? How do? I bough my z with one of the nismo caps. I'm not sure as to how old the cap is

Positive it has enough coolant in the radiator? If its none of that it most likely is the thermostat as was previously stated.

Yea definitely has coolant. I just changed my coolant about 3k miles ago and I have never had a leaking issue. Am I better off putting a different kind of thermostat in?

Yeah if its not leaking you should be set. Honestly I didn't even check mine for around 5k but I stopped at the store and bought some 50/50 and it used at most like 3oz of it cause it was full and then I put some in the reservoir to the max line.. I remember reading about the thermostat and the most recommended ones but I honestly don't remember what it was and don't want to give the wrong info..

if the cap is not holding pressure it will cause you to overheat.... it is only like 23 bucks for a koyo one. the thermostat could be sticking open too.... depends on your budget what you want to do first.

^ if the cap was stuck open the OP's overflow tank would have overflowed and he'd have coolant all over the engine bay.

If the thermostat was stuck open than the car would run exceptionally cooler...I ran without a thermostat chasing some (hopefully) headgasket issues and my car ran at 130degrees albeit I have an aftermarket radiator...the engine runs optimally at 180 to 200 degrees and there is a reason the thermostat opens at that temp and closes at that temp - two way street.

my two cents are replace the thermostat seeing that it'll take all of an hour, replace any coolant and bleed the system AND let us know what you come up with...

If you wanted to confirm that the thermostat is functioning you can put it in boiling water and if opens when it's in the water and closes when you take it out than you know it's not the thermostat...but seeing that they are like $20 just replace it.

Ok sounds like I will attempt replacing the thermostat. Hopefully a pep boys or somewhere local has it. Now to find a write up on it simply because I haven't changed one on a z before.
Thanks for the help

aaaahhhh, didn't think of that..... good point. if it were me i would get the nismo one, but that is just me..... and sit down when you see the price

What in the world makes the nismo one so expensive? What about the mishimoto one that is $70? Or even one pep boys/autozone would have for probably $20-30?
And my other thing is that this being my daily driver I'm trying to install this weekend while Im off of school

opens at lower temp and paying for the name.... if you are wanting to do this weekend, i would do oem and autozone second choice. oem is like 16 bucks from courtesy, so i would expect like 25 or under at a local dealership.... i am sure that autozone one would be fine though

Brother is a tire representative and sees a lot of dealerships everyday so he is going to pick one up for me while he is out.
If I'm correct the thermostat is located right inside the the larger diameter lower radiator hose? Any other car I have seen is located in the upper hose so I just want to double check that.
And one gallon of coolant should be enough to refill the radiator I believe

Drivers side bank - yes, top hose connects to it, 3each 10mm bolts 75 INCH-LBS of torque when you reinstall it. While your tire rep brother is at nissan he should also pick up the gasket used between the therm and the engine block if it isnt included.

BEFORE you get too deep into this you should run this test...

get the car running to where the temp gauge reads normal or a little hotter - feel the top hose(radiator feed) and the bottom hose (radiator outlet). If your thermostat is bad your bottom hose(radiator outlet hose) should be cool(ambient temp) while your feed hose will be hot. This isnt fool-proof because your thermostat may be partially functioning.

Another thing to check, make sure your radiator core/fins are not clogged...

I second the clogged radiator. You may just need to flush the radiator and unclog it. Don't know why I didn't think of that either. Usually if that was the case your coolant may begin to boil though. I've seen that happen a few times to people that use water. Don't think I've seen coolant boil over yet though... Could be worth checking though.

Alright I just let him know to grab the gasket as well.
Im going to check the hose temps in a little

Bealljk- I did that test. The lower hose was cold to the touch and the higher one was reading 200 degrees. So it looks like this guy is my culprit (sorry pic is upside down, when I rotate it it defaults back to this)

EDIT: My brother is getting the thermostat and gasket from Eisenhauer Nissan near us so it will be oem

yeah - that leads me to believe your thermostat is not functioning...

let me ask you this question - do you have any white smoke coming from your exhaust?

I think my car has always somewhat had a smoke. Whether that got bigger recently I do not know.
I know a have a terrible noise that comes from my exhaust
What would the white smoke mean?

You are not turbo'd or supercharged are you?
How many miles are on the car?
Any coolant colored gunk in your exhaust?
If you open your oil filler cap is there anything white in there?
Is your car consuming coolant?

white smoke and your thermostat acting like it is may indicate blown headgaskets...Your combustion cycle is forcing air into the coolant passage and air pockets are building up behind your thermostat and restricting hot coolant from opening the bi-metical thermostat element.