Overheating problems?
 

I was driving on the freeway up a hill and i noticed that the temp gauge started to skyrocket and when i would start to go down the hill the temp would also go down. So i contacted an uncle of mine who knows a bit of cars and he told me it was the coolant temp sensor that must of failed. So i change the sensor and nothing happens! The temp will rise and go back down again. It would reach all the way to H and the engine would be fine, it wasn't hot or anything. Then one day driving home from work, about 2 minutes away from getting home, the car actually starts to overheat. So my uncle tells me it could be the thermostat. So i changed it, and still the same. :confused2: :52:

SOOOO basically..
-When i have the car in park, idling, it warms up to normal temp as it use too
-When i drive the car around the block, like 2 mins, it starts to overheat
-Brand new thermostat
-Brand new coolant temp sensor
-Heater blows hot air, after burping/bleeding the coolant system
-Top radiator hose hot and bottom one cold

Anyone know anything that can be wrong? Almost gonna be a week without driving my precious car, and i can't find an answer to the problem, and i don't want to sell her. :NOOO:

Sounds similar to a problem I had, turned out to be a bad radiator cap. Cap wasn't holding correct pressure so under load I would over heat. Went to advance auto and used the rental tools to pressure check the cap and a new one. Solved my issue.

Therm isn't opening still. They come from the store faulty all the time.

I bought a new cap, drove it, and again, in a quick 2 minutes it wanted to overheat. :52:

Are there any signs of thermostat that could be closed? I'm going to need to be testing any therm i buy before i install them now. :icon30: :52:

I would have mentioned the radiator fans if you would not have mentioned the hoses.
The fact that the top radiator hose is hot and the bottom cold indicates a bad thermostat.
They can come faulty from the store but its not common.
you can always get an oem nissan thermostat pay the extra money will have better quality control.
You can also test the thermostat in boiling water prior to installing it. (or the old one)
As a side not I have seen vehicles not the G35 in particular with obstruction in the cooling system that will cause overheating issues, mainly from using water instead of coolant something to keep in mind.
look at the water pump for failure, there is a weep hole that will leak if the o-rings are shot also something to look at since you have not change that yet.

So the bottom hose shouldn't be cold right? I touch it and it's completely cold.

No it should Not be cold when the car is at operating temperature. Check that there are no coolant leaks. If the thermostat is closed the car will overheat even with the bypass. The bottom hose will be cooler in comparison to the upper radiator hose.
Has this car been driven without coolant just wayer

No it should Not be cold when the car is at operating temperature. Check that there are no coolant leaks. If the thermostat is closed the car will overheat even with the bypass. The bottom hose will be cooler in comparison to the upper radiator hose.
Has this car been driven without coolant just water is there corrosion ?
It sounds like there is some sort of obstruction of the top radiator hose is really hot and bottom completely cold

Oh and the sensor has nothing to do with it. For the most part these dont go bad if the car is overheating you need to be careful how much you push that as there could be bigger consequences.
If it is the water pump it is a pain to change but totally doable check this video.DIY Video: VQ35DE Timing Chain Tensioner and Wate…: http://youtu.be/_BlOcBzpjQA

Put the thermostat in a pot of water and slowly bring water up to temp over the stove. Once it hits 180(?) It should open up.

Escozoo, you never mentioned whether or not the fans are operating!!

Also, the bottom radiator will be cool until the thermostat opens and allows the coolant to circulate. So if you check it too early, it should be cold.

I always like to troubleshoot a cooling problem from its initial cold state and see where and when the overheating begins. Before you tear into it and through more parts at it, maybe you could try it too.

If you start up your car from a totally cold (overnight) state, then open the hood and monitor the entire engine warmup process, you should be able to detect what is failing. Initially, the top and bottom hoses should remain cool clear up until the engine temp gauge looks like it's just reaching normal. If you're in CA(moderate air temps), that shouldn't take more than 5 minutes or so. Then, as the coolant temps rise further, the thermostat should slowly begin to open and allow the coolant to circulate through the radiator. At that point (when the upper hose becomes very warm --> hot), you should no longer be able to hold onto the upper hose and the lower hose should begin to warm as well. After a few more minutes like this, then all the coolant in the system should be up to the same temp, with both upper and lower hoses too hot to hold, at which point the fan should turn on as well. At no point in that process (about 10-15 minutes) should the temp gauge ever read hotter than normal.

If it does, and you have verified the thermostat has opened and coolant is clearly flowing through the upper and lower hoses and the fans are running, then you'd start to look at things like the temp sensor, the radiator cap, and the water pump.

Lastly, and just to be totally cautious, take a look at the coolant for oil residue and at the engine oil for frothy foam, which could indicate head gasket issues.

.02

Okay so yesterday i changed the thermostat for a second time and still nothing! The car warms up to normal temp and the bottom hose is still cold! :mad: Maybe it's just the thermostats autozone sell lol. I'm gonna look into getting one from the dealer.

As for the fans, they work fine. When the sensor detects that the engine is getting too hot, they turn on. But after that point they won't turn off, the engine doesn't cool down with them on. From what i know, correct me if i'm wrong, when the engine is hot and the car is not on, just have the key in the ignition, they should come on right?

Coolant has no signs of oil, nor does the oil seem foamy.

Also, when i drive the car for about two minutes, like mentioned before, the car starts to get extremely hot and wants to overheat! And still the bottom hose is cold as ice! So i keep telling myself its the thermostat? Could i be right?

Seems unlikely that so many could be bad, but it does sound like thermostat or waterpump at this point. Clearly, the coolant is not routing through the radiator, so either the thermostat is blocking it, or the pump isn't pumping it.

Like it was said before thermostat was changed twice chances are thats not it. When the thermostat is stuck closed the hoses dont get hot. Think about where the thermostat is and what way the water is flowing. If the top hose is hot and bottom is cold there is no flow in the system. You can flush the system see if that would help but I would start looking at the water pump