Thread revival! I had the same problem as op. I got a leak in a hose. Car ran hot. I replaced the hose and refilled the radiator with water since I didn't have any coolant handy. Well, it started over heating again about a week or so later. The first thing I did was check all of my hoses and plugs. Everything was right. So I refilled with some coolant that I picked up from a truck stop (cause I was on the road) and it cooled down but was still running hotter than it should be. Well, I got the car home, jacked up the front end, drained all coolant, opened the heater line and refilled. I feel like I bled it well because it filled to the point that it was comin out of the heater line.. Anyway. It's still running warm. Twice the temp needle has gotten to the head of the unbuckled seatbelt light. Well today while I was drivin home it ran warm so I turned off the ac and rolled the windows down and turned the heater to full blast and like magic, it went to normal temps. I ordered a mishimoto cap and thermostat. I'm thinkin that should do the trick.. But has anyone ran motul brand MoCOOL? Any good or no? I went ahead and

 

Ordered a bottle anyway. Wow that was a long post

 

Having the same problem here,my Z over heats when parked or on a street ligth, even faster when I have my a/c on... At first i thougth it was only one fan kicking in, the none of them were working, today I took them out jump them directly with the battery and they worked.... Also veryfied the relays and everything's good...any ligth??? Thanks

 

Im having the same problem with my z.
Ive got 03 with stillen stage 2 supercharger, oil cooler, intake.
My thermostat is new
My radiator is new
when it started i drove 9 hours straight. Every two hours the temp gauge would start to rise and lower randomly but mainly staying hot. Some times it would get hotter in idle going down the road and some times i would get on it and the temp gauge would temporarly drop.
I would pull over, the upper hose was very firm with preasure couldn't even push it, i would release preasure on rad cap. Start up and get back on interstate. Two hours later same thing starts again. I never used the heater the entire time because hevsaid it didnt have it.


So when i got home:
I changed oil, no coolant in oil,
Ive used the spill proof funnel for 3 days i burped the coolant system.
If i rev it to 3500 rpm while burping the heater blew hot.
That was the only time it was hot.
There is a light dark color to the coolant when i use the funnel. It does not look like oil.
The car does not smoke at all!
It ran fine for a in town drive.
No heat still after burping 3 time upwith car on a goo angle.

I started on another trip and it began over heating agin. Very sparstiic going up and down but mainly staying hot. The upper rad hose was under extreme preasure.

No its parked and im broke so ny info on any past experiences anf fixes?

 

Mine did pretty much the same exact thing. Once it cooled off I filled the coolant, which wasnt much, and put some in the reservoir just to be safe. I started it and took the rad cap off and squeezed on the Intel tube a few times, I squeezed it pretty much closed for a second and slowly released, I did this about 3 - 4 times. I then let it warm up with the cap off. Then i put the cap on and turned it off. Later I had to drive and it never got over that 40-45% sweet spot it always stayed at. When I got home I left it in drive and turned heat on max for a min, nothing, ac max, nothing, and back and forth a couple times. It never heated up, and still hasnt started to overheat again.. maybe it had a hiccup, or it fixed itself lol

This z appears to possible fix itself I know, sounds ignorant, but when I first got it the cel came on for an o2 sensor, and the light never came back and I haven't had any problems O.o
You think its weird too? Btw that was 7-8 months ago....