Is my car REALLY Overheating? Hmmm....

[cscotty]

That's the $1Mil question. How do you tell that your car is overheating. The temperature gauge in my car shoots up to the middle within 5 minutes of starting (seems normal), but after that it continues to go up and down, and up and down. I replaced the thermostat and the radiator because they needed replacing anyways and it didn't help. When the gauge goes up past half way, the fans kick in and starts blowing, but at the same time I loose heat in the car.

Had it checked at the mechanic and he says its not my head gasket (yikes!). Before I start throwing extra parts at the car, how do I know if my car is overheating? Are there any physical symptoms that I should see, or do I put my full trust in a gauge (that I had to replace before because of the same problem). Just want to know before I go throwing parts at the car.

Thanks,
Scott

[galantlvr34]

Well since you arent getting heat in the car it seems like there is air in the system.I would try bleeding the system out and see what happens.

[cscotty]

Thanks for the reply. The complete system was bleeded when the radiator was replaced. Bleed, flushed, back flushed. It gets heat as long as the fans stay off. But the when the needle passes the halfway mark and the fans come one, the heat begins to cool.

As for detecting if my car is really overheating, is there any visual confirmation that I should notice?

Thanks,
Scott

[galantlvr34]

When the fans kick in the needle on the gauge goes down right?The heat shouldnt get cool when the fans kick in,which is why it sounds like a circulation problem.

[cscotty]

No the gauge continues to rise. When its about 3/4 of the way to the top, then it just drops back slightly above half way. It'll stay there for maybe 5 minutes and shoot back up to about 5/8 of the way, then 6/8, then 7/8. It never touches the red, but it will stay at 7/8 of the way for a good 20 minutes. This all occurs within 30 minutes of driving the car.

Thanks,
Scott

[galantlvr34]

Maybe it is the thermostat you put in it,some of them have higher temperatures then others.When the fans kick in it should cool down though,that is usually when the thermostat cracks open.

[cscotty]

Doubt it. It was acting just like this before the thermostat changed. Im gonna try changing the Coolant Temperature Sensor and see if that does any good. Any other suggestion?

Thanks,
SCott

[tamim13]

Before you throw any more money into this, read this thread -

https://www.thegalantcenter.org/showthread.php?t=41977

Also, I suppose you have more than 100K miles on the car?

[Gotti]

There's 2 coolant temp sensor. 1 for the gauge and 1 for the ecu and fan controller.
If gauge is correlating to the fans kicking on I would look into coolant level or thermostat.
One way to check it is letting the car sit over night. Next morning open the radiator cap and top off coolant if needed.

[tamim13]

There's 2 coolant temp sensor. 1 for the gauge and 1 for the ecu and fan controller.
If gauge is correlating to the fans kicking on I would look into coolant level or thermostat.
One way to check it is letting the car sit over night. Next morning open the radiator cap and top off coolant if needed.

Are you sure there are two coolant temp sensors on the 8g? I was told there is only one, which is the brass one. For my car, I know for a fact that the car is actually over heating and there is nothing wrong with the gauge, because I have an ultraguage and have actually measured the temps in my engine bay manually.

[finald8ta]

Ok I have an ultra guage as well and there is 2 sensors if u disconnect the wire for the cluster you will still get a reading on the ultraguage,

My temp with the ultrgauge are 198/210

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[tamim13]

Ok I have an ultra guage as well and there is 2 sensors if u disconnect the wire for the cluster you will still get a reading on the ultraguage,

My temp with the ultrgauge are 198/210

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Yeah those are exactly around my ultraguage readings too, but I was told that it's not two different sensors, but just that the ultraguage is just reading the temp directly from the ECM, which also stores the temps to turn on and off the fans, control the coolant circulation etc. The brass one that I was talking about and the one you probably disconnected is the one that controls the guage on our guage cluster.

I'm now researching doing what g-spot said. I'm going to look at replacing the ECM relay. If that doesn't work either, I will think about replacing the ECM and seeing.

[finald8ta]

Yeah those are exactly around my ultraguage readings too, but I was told that it's not two different sensors, but just that the ultraguage is just reading the temp directly from the ECM, which also stores the temps to turn on and off the fans, control the coolant circulation etc. The brass one that I was talking about and the one you probably disconnected is the one that controls the guage on our guage cluster.

I'm now researching doing what g-spot said. I'm going to look at replacing the ECM relay. If that doesn't work either, I will think about replacing the ECM and seeing.

If the brass one has one wire on it then its the guage only, ill get a pic up here shortly

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[finald8ta]

Ok Im Gona clear this up very easy, the 4g64 motors have two water temp sensors,

One controls the guage and the other goes to the ecu witch controls the fans


It's right below the cam sensor
Here some pics

Controls fans, ecu, ect



See the -40

That is all

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[tamim13]

Yes, the one I replaced was the one in the 1st picture. The second one is inside the ECM?

[finald8ta]

the 1 in the first picture is for the ecu, the other 1 is located on top with 1 wire sticking out of it that 1 is for the gauge cluster, I will post a picture of that 1 later

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[tamim13]

Which one did you disconnect, to cause your temps to drop to -40? The ECM one?

[finald8ta]

Which one did you disconnect, to cause your temps to drop to -40? The ECM one?

The one in the first pic, the other is located on top of the near the injector on the water houseing near the tstat, that one controls the water temp guage in the cluster. Gime a min to get you a pic

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[finald8ta]

This is the sensor for the gauge cluster only

See that little guy in the center of the pic, my wire came loose trying to take a pic

You can see that it on top near the corner of the valve cover and under the wire harness

The ultraguage reads every sensor going to the ecu


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[tamim13]

Thanks for the pictures. So your problem with overheating is still not fixed after replacing both sensors am I right?