Weird cooling issue?

[Krew126]

Ok, so after about 5-10 minutes of driving my car, it will sometimes start to idle higher at stoplights and take a little while to come back down.It only does this if you drive it for about 10 minutes. The car will start to idle at 1,000 rpms or a little over.Also, say I'm cruising in 4th at 40 mph, and I put it in nuetral not giving any gas, the car will slowly raise the rpms and then about a second or 2 later it will come back down to 1,000.

Now you ask, what does this have to do with cooling?Well, when it runs like this if I turn the car off and get out, I will have coolant rushing into my overflow tank with the smell of burning coolant when you open the tanks cap.

Keep in mind, this only happens sometimes which is why I have no clue what it is. And when it runs like this, the temperature gauge shows no signs of overheating at all. If anybody could help I'd really appreciate it, thanks.

[Gabes13]

What condition is your

Temp sensorTPSandRadiator cap

in?

[biggie]

Few other possible things.

Bad thrermoAir bubble in system

For the idle, was it swapped to manual from AT and still have the AT ECU in it? If not then IACV I would guess.

[sean@z1]

I had a similar problem and i had to replace the thermostat and coolant temp sensor and the idle sounds like you need to clean the Idle air

[Chris28]

Kind of related, if you replace your thermostat use an OEM Nissan one. Not the Stant crap that Advance Auto sells. Before you put it in, use a baby asprin to keep the thermostat open. This allows the system to bleed properly when you are filling it, and once the coolant starts circulating the asprin will dissolve with no ill effects to your coolant.

[Krew126]

Thanks for the quick responses everybody.Pandapants:For the sensors I will have to check them, and the radiator cap sometimes would bubble a little coolant out when the coolant would rush into the overflow tank (Was planning on getting a Blitz cap).

Biggie:At first I was thinking the thermostat, but then thought it could be something different. If I do change it, I plan on getting a nismo one, unless somebody has reason not to. And the car was AT now MT with a MT ECU.

Sean@z1:I'm going to to check the coolant temp sensor right now.

Thanks for the help guys. Just wondering though, is there any special way to tell if the sensor is messed up? Sorry little bit of a noob.