# Another overheating issue



## gtoarmuth (Jan 24, 2010)

I have a 2005 GTO with 40,000 miles. Just recently it has started overheating. I am from Indiana so the temperature is around 30-50F this time of year. Since it is winter I preheat the car for about 10 mins before I leave, when I get into the car the air blows cold but the engine is at operating temp, after driving down the road the heat would suddenly start. 

I got curious and started the car cold to see how long it would take to blow heat or if the engine would start to overheat. The temp gauge started slowly climbing up towards the red, fans turn on, still blowing cold air. Then I ran the RPM's up to 2,000 to simulate driving conditions and the temp returned to normal and hot air started blowing. My best guess is the water pump. Is it possible the radiator cap is not sealing causing an air pocket? Has anyone had this issue?


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## GTO JUDGE (May 14, 2005)

gtoarmuth said:


> I have a 2005 GTO with 40,000 miles. Just recently it has started overheating. I am from Indiana so the temperature is around 30-50F this time of year. Since it is winter I preheat the car for about 10 mins before I leave, when I get into the car the air blows cold but the engine is at operating temp, after driving down the road the heat would suddenly start.
> 
> I got curious and started the car cold to see how long it would take to blow heat or if the engine would start to overheat. The temp gauge started slowly climbing up towards the red, fans turn on, still blowing cold air. Then I ran the RPM's up to 2,000 to simulate driving conditions and the temp returned to normal and hot air started blowing. My best guess is the water pump. Is it possible the radiator cap is not sealing causing an air pocket? Has anyone had this issue?


My thought is a sticking thermostat. The radiator cap is the yellow screw on type and its not under pressure. Perhaps when you are accelerating RPMs the pressure is forcing open the thermostat and when the pressure subsides the T-stat sticks?


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## gtoarmuth (Jan 24, 2010)

The only thing that is tricking me is I don't have heat. I would think regardless whether the t-stat is sticking or not I would have flow to the heater core. the water pump is turning but at idle it asks like there is no flow. I know the t-stats can cause random issues so I will look further into that, thanks for the post.


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## GTO JUDGE (May 14, 2005)

If you have a faulty thermostat you won't get heat. You may experience slight warm with mostly cool air.


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## gtoarmuth (Jan 24, 2010)

So Its possible to overheat and blow cold air? I will replace the cap and if that doesn't work than the thermostat. I will post back with the resolve. Thanks again.


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## gurvinerjeff (Jan 9, 2009)

This sounds like low coolant level. There is not enough flow to the heater and there is not enough flow to cool the engine. Check the coolant level!!!


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## GTO JUDGE (May 14, 2005)

You can do a touch test on the upper radiator hose... If after sufficient running time the upper hose is not hot or just barely warm that could indicate a faulty thermostat.


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## jpalamar (Jul 22, 2008)

Replace your t-stat. It is probally not closing all the way. Mine had the exact same symptoms. FYI... don't go to PepBoys for one cause they lasted 3 months each for me when I needed one in a pinch. Advance Auto has nice fail safe ones or go OEM.


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