Overheating

cre · 07-01-2007, 04:40 AM

Yup it happens. I just wanted it made clear that there are other things that can cause this problem besides a BHG.

Let's not forget that a faulty rad cap can cause a BHG.

For the benefit of those interested: The radiator is a pressure valve. The higher the pressure in the cooling system the lower the boiling point. Reduce the pressure the boiling point rises. So when a bad radiator cap starts venting coolant too soon it can release enough pressure that your coolant actually starts to boil. Water vapor takes up a lot more room than condensed liquid and the excess volume has to go somewhere. Once this happens both the coolant mixture and water vapor begin purging out of the system through the overflow.... they've got to go somewhere. As this continues the coolant mixture begins boiling more and more rapidly, and as such the purging gains momentum. You can actually end up running on less than half of your coolant in a couple minutes. If you're not paying attention you can overheat big time and then... you guessed it: BHG.

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07-01-2007, 04:40 AM	#8
cre Toyota Racing Development Join Date: Apr 2007 Posts: 5,038	Yup it happens. I just wanted it made clear that there are other things that can cause this problem besides a BHG. Let's not forget that a faulty rad cap can cause a BHG. For the benefit of those interested: The radiator is a pressure valve. The higher the pressure in the cooling system the lower the boiling point. Reduce the pressure the boiling point rises. So when a bad radiator cap starts venting coolant too soon it can release enough pressure that your coolant actually starts to boil. Water vapor takes up a lot more room than condensed liquid and the excess volume has to go somewhere. Once this happens both the coolant mixture and water vapor begin purging out of the system through the overflow.... they've got to go somewhere. As this continues the coolant mixture begins boiling more and more rapidly, and as such the purging gains momentum. You can actually end up running on less than half of your coolant in a couple minutes. If you're not paying attention you can overheat big time and then... you guessed it: BHG.