PLZZZ HELP!!

I posted one thread about my car overheating last week. So here i go again;
i changed my temperature sending sensor and got the same temperature as i had with my old one. now what i think the problem is the new thermostat i got is bad or some thing, because the upper radiator hose is warm as hell and the lower one right before the thermostat is cold as it is. The new thermostat i got was from autozone and i bought it last week, but when my mechanic changed it he said the new thermostat is not openning and the car is over heating. After driving my car 2-3 miles under 50mph, then it starts to overheat. I dont have a leak in radiator or in water pump and my coolant level is where it should be, and i even ran my rad. fans manually but it didnot make any difference. SO ANY IDEA WHAT COULD IT BE??????

 

If you changed your thermostat and still over heating, you might have a problem with the water pump. The pump or the belt to drive it might be bad. just a thought.

 

It's run off the timing chain.

Ding ding ding we have a winner.

 

if anyone is overheating then it could be...

radiator (could be clogged (internaly or externaly (front or rear))).
waterpump
thermostat
hoses
fans (not spinning at correct speed or not spinning at all).

sensors are also a possiblitiy, but not likly depending on the above.

 

Another problem is my fans dont even run, i have to run them manually by taking that switch off of that coolant temperature sensor. I thought my sensor was bad so i even bought a new coolant sensor, and a new temperature sending sensor but that didnot make any difference. is there any thing else to check for the fans besides that thermostat.

 

Was the system bleed correctly? Run the car untill it's hot with the radaitor cap off, increasing RPM's until the fans turn on. That will assure all the air is out and the pump is circulating the coolant correctly.

You could also have a blown head gasket......

 

If you turn the AC on, do either/both of the fans turn on?

 

my head gasket is in great shape, and no my fans dont come on with tthe ac running.

 

I will try this tonight.
thanks.

 

I think either the thermostat is bad or you have air in the lines. Either one of these problems would cause the lower hose to be cold. The system could be air locked or the t-stat is not opening. Try what NJTom said, if that does not work then I would guess its your thermostat.

 

I just bought a new tstat today. hopefully i ll change it tonight.

Thank you guys, i really appreciate your help.

 

I have a friend who works for a company that manufactures all thermostats for our VQ engines. He said that a lot of aftermarket thermostats for VQ currently sold in the United States, including ones available at autozone, are made in China or some other Asian countries and their quality/design is seriously questionable. He also said that the one sold at thepartsbin.com is the one they manufactured.

If your issue turns out to be a thermostat, I suggest that you get an OEM one.