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Discussion Starter #1
I had an overheating issue about a week ago. I took the rear overflow cap off and let the car sit a few minutes, there was some pressure and some coolant squirted out, but it seemed fine up until today. After driving approximately 45 miles on the expressway, I got off the exit and noticed the temp gauge creeping up slightly at a stop. I immediately pulled over and took the rear overflow cap off. The coolant was almost boiling. I let it cool off a few minutes and decided I better limp it back home. I stopped a couple times along the way to cool off. On the expressway it stayed right at midrange (creeping up slightly once in a while, but dropping right back down to normal.) The radiator fans are kicking on and the heat is intermittent (as I was running the heat full blast while going home). It immediately started to creep up quickly when off the expressway. I limped it into the mechanics shop, but he wont be able to look at it until monday. So to sum up:
-fans are kicking on (both)
-there is coolant in the system but it ends up getting almost boiling hot and seems to have a lot of pressure, but it is NOT overfilled, but the fluid does vary in the overflow upon checking
-the HVAC heat is intermittent while it appears to be slightly overheating
-i see NO leaks from the radiator (I have no front plastic so it would be more obvious)
Does this sound like a sticky thermostat, or an air bubble in the system? There is no visible coolant in the oil to indicate a headgasket, nor seeping coolant anywhere in the back.
 

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What kind of coolant have you been adding? Or have you just been adding water and no coolant?
 

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It's most likely a bubble. Search for the bleeding procedure and take care of it. If it happens again then investigate further. This is a very common problem that car present it's self at any time.
 

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Discussion Starter #4
Pomonified: I was just adding regular green 50/50 premix (there has been green in since I bought it) Dev: I will try the jacking up the car tonight and try it later tomorrow, if no luck ill try the actual bleeding...is it common that an air bubble would randomly develop. It seems like air would have to have gotten into the system somehow
 

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Pomonified: I was just adding regular green 50/50 premix (there has been green in since I bought it) Dev: I will try the jacking up the car tonight and try it later tomorrow, if no luck ill try the actual bleeding...is it common that an air bubble would randomly develop. It seems like air would have to have gotten into the system somehow
Yes it can randomly happen. In my case I completed a 2zz swap and about one year later developed a bubble and an overheat condition. I burped it and it hasn't come back in four years.
I suspect that a bubble gets lodged somewhere inconspicuous but does not cause a problem until it moves like an embolus to the water pump where it causes cavatation.
It's just the nature of the bleeding and therefore you may find yourself bleeding it a few times after a coolant flush.

If it persists then we must investigate other causes.
 
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