I did a search but didn't find anything that was similar to my situation.

03 G35
Greddy TT for more than a year now, not a single issue with heat.
Earlier this summer I swapped out the stock rad for the big koyo.
Ran all summer + many HPDE with NO overheating issues at all.

I live in Ottawa, Ontario Canada.
Tonight is a chilly night, 10c to be precise. Take the car out to meat some friends, haven't touched it for 2 weeks since the last time I was at a HPDE actually.

Car starts to over heat, I park it, the temps drop.
Check under the hood, fans are OK, coolant in the overflow tank (a normal amount), check the coolant plug on the bottom of the rad, still there. Check the hoses (Samco) seems fine.

I also noticed no heat was coming from the vents, so I crank it up, nothing. No heat just cool air.

Take the car back out to go home, does it again, but this time I let it get hot, then asif the thermostat just opened and dumped cold coolant into the motor, the needle drops back to normal. Weird.

I beat on the car a bit, it's normal, I cruise normally, it starts to creep up again, but then goes back down to normal. It did this all the way home, car still ran fine, no smoke, no smells. Still no heat all the way home...

Any thoughts on the issue? Do I need a NISMO thermostat in this cold climate to open at a lower temp? Air in the system all of a sudden?

Thoughts? Sorry it's long, it was just a brain dump of the events tonight.

Thanks in advance!

 

Sounds like your thermostat......I dont think its air in system because you said it was fine in the summer.....as long as you did not drain the system recently. Sounds like its not opening at the correct temp.

 

Yeah thats what I was thinking, once it hits "temp" it just drops, and If i cruise, let it cool down, it creeps up again until it reaches a certain temp. I assume its opening and closing?

Would a NISMO open at a lower temp and solve this issue? Instead of waiting till 190F or whatever OEM is?

 

I have this theory for some reason, the big rad is keeping the coolant too cold (on these cold nights) and it's not opening in time thus the temps of the motor start to rise.

Im gunna go for a spin tomorrow when it's warm and see if the issues happen above 10c

 

i have to tape off part of my radiator on my racing scooter in cool temp bc it never comes to operatring temps even with my thermostat. differnt scale, but same principal.

 

Interesting, I'll update today, got a golf game soon

 

i agree sounds like a bad thermostat. i ran into the same problem w/mine. it was overheating so i installed the new thermostat. i was thinking about the nismo t-stat but if you do your research it only opens 154 vs 170 oem? plus its 118+(nismo, no warrantee) vs 23 bucks @ autozone my opinion, not worth it.

i purged the bleeder valve (passenger firewall) and burped it numerous times and i didnt see any leaking. im taking mine to a shop because i tried everything. my advice is start off w/t-stat. then burp n purge your lines to get rid of air pockets.

heres how to purge you coolant but i dont think thats your problem
https://my350z.com/forum/forced-indu...nightmare.html

gl w/your problem

 

I highly doubt this is the issue. with two turbos under the hood, these cars get HOT. Keep in mind, your radiator is tucked behind your intercooler and AC evaporator core. It isn't getting direct flow.

You either have a bad thermostat, or need to rebleed the system

 

Maybe its the gauge?

 

Heres some food for thought.

So after golf today, I figure I'm gunna take the car out and see what it does. Start her up, car shows 18c outside. Warm.

Let it warm up, everything looks normal.

Take it over to my brother in laws, beating on her nicely, sideways full out every corner, temp needle looks normal, nothing wrong.

Get to my brother in laws, he has an ODB II reader, we plug it in to look at the temps, everything looks normal at idle.
We go for a rip, full out trying to get the car to over heat, temps ranged from 185-200, nothing extreme, the needle still looked normal, never rised to hot.

Further confirming my " Radiator is too efficient" idea.
We go get dinner, same thing, drifting corners, full out...nothing, everything looks normal.

So as Im coming home after dinner and whatever, beat on her some more, she takes all I can give her, I'm coming into my cresent, the car temp starts to climb again, the temp is 19c outside, but the car is showing hot again.

Pop the hood in my drive way, everything is normal, no problems, let the car idle, fans are 100% on and blasting, turn on the hot air, jam it up to 32c, nothing really hot comes out. So I turned it off.

So....I dunno. When the car is hot, and being driven on a hot day it's fine, it eats it up and loves it.

P.S. When I unscrew the coolant bleeder cap, and press the valve pin in, nothing happens, no hot air, not coolant, no nothing. I atleast expected coolant to come shooting from their which is kinda strange. But there was nothing.

 

Air bubble in the system.. you need the special funnel.. i bought one.. worked like a charm.. was having the same problems with my koyo

 

http://www.amazon.com/Lisle-24610-Sp...3398399&sr=8-1

 

And looks like this.......If its air that is trapped in there....I would not beat on it until you get it out

 

Thanks guys, a friend of mine has one of those, I'll give it a shot.

 

I can promise you your radiator is not "too efficient"

rebleed your system

 

I just don't understand how after months of the car being rock solid there is air in the system.

 

yup.. thats her.. went to Autozone guy told me i was crazy.. went to my local parts supplier and they got it for me.. worked like a charm.. heat is back.. no overheating

 

it happens man..

i had my issue 07-11-2006 ... bleed the system

https://my350z.com/forum/forced-indu...hlight=coolant

car ran fine.. never overheated, but my heat never worked again..

then 08-24-2009 my car started to overheat again

found this thread https://my350z.com/forum/forced-indu...ghtmare-2.html

bought the funnel.. worked like a charm.. heat came back..

now that was a little over 3 years.. can you imagine that? i had another bubble i never really got out and it took 3 years to get worse

 

lol ****...thanks doug, I'm gunna borrow my buddies and give it a shot...

weird stuff.

Is it as simple as put that funnel on, fill it up, lift the front of the car, start it, let it come to operating temp and wait for the bubble?

 

you need to fill the funnel and open up the bleeder in the line near the firewall and let the air out. Close up the system, get car up to temp, turn heat on, cool it down and repeat