There is no debris in the systel. I had Firestone and Infiniti flush and bleed the system for me. The heater blows hot as well. It overheats at times, and then at other times it does not. Im wondering if they need to just drain the system and fill it with a vaccuum system? This would absolutely ensure there is no air in the system right? I just want to get it all figured out, as this one is my wifes car and she drives it with our son in it and cant have it having problems. Thanks for the tips so far!


Also, it seems to me the water pump is fine. They are chain driven and either work or not. It iis fine in cooler temps(80-90) and if it were that, it would overheat in any situation.

 

I do know all 03s have a mechanical and an electric fan. The electric in the front turns on when A/C is running pushing air and the mechanical is behind the radiator pulling air through. My mechanic friend told me the issue sounds like a air circulation issue. He said clean the radiator from the front and back. If that don't work maybe need to replace fan clutch.

 

I have confirmed it still seems like air. It will do it after I brake semi hard or after a quick turn. After driving for a minute....it is back to normal.

 

2003.5 have dual electric fans...just becuase you had a shop flush the system does not mean that you do not have air in the system. Also, it could get introduced to the system via a small leak somewhere.

If you buy the spill proof funnel you will be able to watch the air bubbles come out if there are any.

 

will a vaccuum fill emilinate any and all air in the system? I cant seem to get it out any other way and it randomly overheats.

I started the car in the 103 degree weather yesterday and let it idle 20 mins....stayed below center. Drove around for a while and was fine. Then I hit the breaks and it crept up and then after a few miles went back down. Also, if you idle somewhere for a shile, and then start driving the guage will go 3/4 up, maybe a bit higher, and then will start to go back to normal after driving 40 or so. Then at intersections etc it is fine again.

 

a) air bubble in system
buy a spill free funnel like this: http://www.summitracing.com/parts/LIL-24610/

b) you have a fan that is intermittently failing

c) t-stat that is sticking

d) Water pump is starting to fail

e) you have a small leak introducing air into the sytem somewhere (a pressure test should eliminate this as an option though)


I still think you have an air bubble in your system but it could be any of these things.

 

Well, took the car back to Infiniti yesterday and had them flush and vaccuum fill the system. They drove it and let it sit running for over 2 hours(in 100+ degree weather), didnt get hot. Wife picked the car up, and on her way home guage pretty much topped out and she had to pull over to let it cool.

Infiniti thinks I may need a bigger radiator due to the turbo system. I dont see why this would make a differance. I have 2 ideas.....

A) could the radiator be going bad/have a intermittant blockage and need replaced? The car has 180k on it and as far as I know, it is original.

B) I may replace the thermostat with a lower one. Is stock on these cars 170? Do you know of a place I can buy a 150 or 160?

 

Mishimoto makes a 154 degree thermostat vs the stock 170. Im thinking this would greatly help me out being in these hot *** temps of nebraska. It doesnt do it towards night or in the morning when it isnt the heat of the day.

http://www.importpartspro.com/mmts350z03.html

 

Also, I am thinking of trying to put on a 1.3 bar radiator cap to increase the pressure of the coolant system, and raise the boiling point. Could this be a cost effective possible solution?

 

Stock rad cap = .9 bar
I have a 1.2 bar which is the same one the 300ZX turbo version uses. $12 at the dealer.
I don't think this will solve your problem.

How much power are you putting down? Unless you stompin' on it the stock cooling system does a very good job.

Stock thermostat opens at 170* F for the dual electric fans and 180* for mechanical fan equipped cars. Buying a NISMO with 154* will not change a thing. The problem is - the longer this persists the more likely you are of warping your head due to excessive heat.

If you aren't leaking anywhere and don't have air in the system I would blame the thermostat or possible electric issue going on with the fans. Even new T-stats can stick. Thats why its always a good idea to test them in a pot of boiling water before you install them on your car.

How is the level of the overflow? Does this change at all?

When the temp gauge needle first starts to move do you get out and check the fans, overflow, etc?

 

It is possible that the radiator is a problem, but I don't see why the issue would be intermittent like it is.

 

fans and overflow are both good. It will boil in the overflow tank if you let it get too hot. Fans always come on just fine. I am not stomping on the car, just normal city driving. There are still no leaks and the only time it has lost coolant is when it was allowed to boil over. I am completely lost at this point.

 

Turbo system? What? Are you possibly on KCSR.org?

A turbo system could most definitely be the cause of all this. It probably would have helped greatly to note this in your first post because I think many of us were led to believe this was a stock, woman driven G35.

1) Turbos create a lot of HP = HP creates a lot of heat = Your turbo G35 creates a lot more heat than an NA G35. Even during just normal driving, it could have an impact depending on the spool range of the turbo.

2) Where's the intercooler mounted? If it's like most every intercooler, it sits in front of the radiator. That obviously impacts air flow to the radiator.

3) Since the car is an auto, the lower portion of the radiator is also taken up by the tranny cooler.

4) Turbos increase underhood temps dramatically, heat soaking all sorts of stuff including the radiator.


So yes, it is very possible and likely that the turbo is the cause of your problems. One of the first mods with a turbo system should always be a larger capacity radiator.

 

My guess is because it's been 100-105 degrees with high humidity in the Midwest for almost the past 2 weeks which is a bit out of the norm for July. Temps within 3 feet of the pavement are probably around 120ish. If this is the guy I'm thinking of, he hasn't owned this car but for maybe a month.

 

we have had the car for roughly 6 months, just found a deal on another that we are getting. I am on kcsr.org as well. I am ordering the aluminum radiator for it tomorrow to replace it with a higher capacity. I put the 300zx radiator cap on today to raise the pressure 4 psi and that actually helped. But just to be safe, I am replacing the radiator with a higher capacity one as well, looks like it holds 4 more quarts than stock and should help a ton.


Sorry I didnt mention the turbo before, it completely slipped my mind.