Hi MY350Z.com,

I've searched through numerous of threads and can't find a flat out answer. I just bought my '04 350Z Track edition 2 weeks ago and I've already ran into my first problem. Temperature gauge keeps reading hot-beyond hot unless if I'm driving a steady 45mph or faster then it'll come down a little or back to normal. I've checked my coolant level, it's fine as well as no smells. Fans are working. I popped the hood and notice the car seem very hot and the fans didn't kick in. About 5 mins later I manually tapped the fans with my hand and they kicked right in. This is a very frustrating situation. Why is that when I drive the car at 45mph or faster it cools down? Please help me guys! I live in Florida and the last thing I need is cooling problems. Thanks!

 

that should tell you something.......you more than likely have a bad fan, and really on the second part? think about it, you are driving and forcing air through the radiator

 

I agree with travlee here, it's probably a fan not working that is causing your z to overheat.

 

lolol

Proof the American education system has failed.

 

This stuff isn't that complicated is it? I mean, if you have something that isnt working, you hit it and it works, you should probably look there first....

 

reason its over heating is because the car needs electrolytes. its what cars crave.

 

Update: Fans are working like normal again but car is still overheating. Coolant isn't low neither are there leaks or anything.

 

Thermostat could be stuck closed. When the car is at operating temperature do both radiator hoses have pressure?

 

You can also feel the hoses to see if they have fluid moving through them, should get hot. I think that's what I did to make sure the thermostat was opening during the coolant flush/thermostat replacement.

 

When the gauge shows hot, feel the lower radiator hose. If it's cold, you need a t-stat. If it's hot, you have another issue. Could be as minor as air in the system.

 

are you running the A/C? mine used to overheat when i used the A/C because the condenser fan didnt turn on. took it apart and found that the dumbass mechanic who worked on the car before i bought it bent the pins on the plug for the fan. I bent them back and all is well. I have an extra fan motor (brand new in box) if you need it.

 

Update: Both hoses have pressure and I've bled the system again. I just took the car for a 20 minute drive around my town and the temperature gauge just kept going up and coming back down to normal. On another note, the temperature gauge didn't go extremely high like how it did before. There might possibly still be air in the system I'm thinking or I definitely need a new thermostat.

 

Did you pressure test the system?
Check water pump for play in the shaft?
Check your radiator cap?
Clean off or replace the temp sensor?
Replace the thermostat?

All basic cooling system troubleshooting.

 

Checking the water pump in a VQ35 is not basic trouble shooting. That's major work. If you're gonna check it, replace it.

 

Too true. Just pointing out it might be a pump issue as yet another possible point-of-failure.

 

Thermostat could be the issue...the other issue I've noticed from Nissan is the radiator cap... of all things...when you overheated before, did you have it steaming and spraying around the radiator cap? If so...it's shot and not sealing, as it gets up to temp, it's losing the seal and creating a vacuum freeway for air to build up in the system! ...I know sounds stupid...but it's 10 bucks to find out!
Also, if you have a stock radiator that has overheated, there is an excellent chance that it may have a small crack that is sucking in air. But in order to completely get all the air out of the cooling system, generally the standard "burping" technique is NOT enough! It needs to be vacuumed out then refilled, if the system won't vacuum out completely, you have a crack and or leak in the system!

 

There was a recall on the fans. Mine failed (also a 2004 model) and were replaced under warranty years ago.

Your air conditioning will only produce cold air if you are moving, right ? Sure sign of bad fans.

https://my350z.com/forum/350z-roadst...an-motors.html
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Update: Thank you everyone for all your help! I ended up vacuuming and refilling the coolant and it seems to have fix my problem. No more overheating, thermostat is where it should be. I will eventually get around to upgrading my whole cooling system this summer.

 

That's good to hear.