So ive had my 350z for about 2 years now bought it at 98k miles, it is currently at 117k miles. I am having a problem with my car as it overheats. I checked my oil and its fine no white exhaust smoke so im thinking maybe its not the head gaskets. When we check the radiator after a while the coolant starts to shootout almost like a fountain it seems like it has excessive air in it and it pushes out all the coolant in the radiator out the radiator cap(without it being on of course) it doesnt overheat when the cap is off but as soon as i put the cap back on it starts to overheat. I dont know if anyone else has had this problem. And if so what they did to fix it or any guesses as to what it is. Any help would be appreciated.

 

Are you saying coolant shoots out of the radiator (cap off) when the car is cold? If so, then I would think combustion gasses are getting into the coolant system, likely a failed headgasket.

However, if you mean you put the cap on, after the car had been running without it, then proceed to remove it, and then coolant spews out... that is normal because by putting the cap on, with the coolant hot, you have pressurized the system.

If what you're experiencing matches my second explanation, you may need to bleed air out of the system (there are guides on here to show you how).
Although I'm not sure exactly how fast your system is overheating from cold to hot? Also, ensure your radiator fans work (turn on AC) and check.

edit: One more thing, does your heater work? A cold blowing heater may also indicate air in the system.

 

The coolant starts to erupt after it reaches the medium heat and it stays there even tho the coolant is erupting, as soon as we turn it off and out the cap back on it starts to overheat and fast

 

Ok, the coolant should not ever spew out with the cap off the entire time, whether hot or cold.
I know this because when bleeding the system, the car will reach full operating temp, yet you still have the cap off, so you can add coolant as air leaves the system.

I can almost certainly say, you need a new headgasket.

From your description it sounds like it doesnt shoot out when cold, but does after warming up (cap off the entire time). Well, as the engine heats up, perhaps the headgasket expands, creating a gap, and allowing combustion gasses to escape through the system.

 

I jad a bad feeling it would be that again! My best bet would probably be selling off the 350z already fixed the gaskets once before twice will be overkill! Thank you for the help.

 

Sorry about that man, hope you can figure it out. I havent heard of headgaskets being a common problem with these engines.

Did the engine overheat on you before this issue occurred?

You say this is the 2nd time replacing it, did it overheat the first time as well?
Just trying to think, that if the headgasket it bad again, and was installed properly, perhaps your head is warped, not allowing the gasket to seal properly.

 

Yes the first time it overheated as soon as i turned on the heater and the mechanic who fixed it replaced the head gaskets, but the car kept overheating even after he replaced them, he then bled the AC system and it worked just fine for about 2 weeks then soon after i again turned on my heater and it started overheating so we pulled the car all the way back home. Ive let it sit there i tried bleeding it but im not too sure if i did it correctly. And the reason it was bled the first time is because we had replaced the evaporator core.

 

Well, the headgasket is definitely bad. And that many times being over heated, I would think the head needs to be removed, and inspected by a machine shop.

As for overheating when turning the heater on, I'm not sure. Possibly a thermostat issue. Maybe wait for someone else to give some feedback as well, before making a decision.

Your mechanic should not have returned the car back to you, with it still overheating. I'm not sure how well you trust the mechanic, but dont let them 'take you for a ride'..

 

If the car overheats when you turn the heater on, it just means there's still air trapped in the system (usually the heater core). If you hear a short rush of bubbling liquid coming from the dash when you first fire up the car, you still have air in the cooling system. These engines are notorious for being difficult to bleed air out. The old fashion way of bleeding the coolant system is not applicable with this engine, you need to pay close attention to the instructions in the factory service manual.

Sorry to hear about the troubles. Removing the heads on this type of engine is a lengthy process.
Good Luck!
-Icer

 

My car was over heating, and it turns out it the fuse to my radiator fans was blown out