COOLANT TEMP/PRESSURE RELATIONSHIP ???
10 October 2008, 03:32 PM
#1
COOLANT TEMP/PRESSURE RELATIONSHIP ???
One for all you physicists out there...
How much pressure is present in the cooling system when, say, 50/50 mix of tapwater/antifreeze is at 100deg C.? Is it significantly less than 0.9bar (13psi)?
I ask this, because I've just plonked my OEM 0.9bar rad cap in some boiling water (but with no antifreeze added), and the cap's spring didn't contract - i.e. open - at all!
How much pressure is present in the cooling system when, say, 50/50 mix of tapwater/antifreeze is at 100deg C.? Is it significantly less than 0.9bar (13psi)?
I ask this, because I've just plonked my OEM 0.9bar rad cap in some boiling water (but with no antifreeze added), and the cap's spring didn't contract - i.e. open - at all!
Last edited by joz8968; 10 October 2008 at 03:34 PM.
10 October 2008, 04:24 PM
#4
Great thanks - understand that.
So regardless of the coolant's temperature, it could be - within reason - at any pressure? And if that pressure happened to be more than 0.9bar then - because the spring's resistance to compression is rated at 0.9bar of pressure - this greater pressure acts on the underside of the cap, forcing it up by compressing the spring, which then allows the over-expanded coolant out via the expansion tank's overflow hole, yes?
So regardless of the coolant's temperature, it could be - within reason - at any pressure? And if that pressure happened to be more than 0.9bar then - because the spring's resistance to compression is rated at 0.9bar of pressure - this greater pressure acts on the underside of the cap, forcing it up by compressing the spring, which then allows the over-expanded coolant out via the expansion tank's overflow hole, yes?
Last edited by joz8968; 10 October 2008 at 04:28 PM.
10 October 2008, 04:46 PM
#5
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yep. i see you have also asked about head gasget pressures. what is the exact problem? it is possible for the cap release valve to go faulty and release to early but it unusual
10 October 2008, 04:50 PM
#6
Yup dead right. 
The excess coolant then gets transferred to the overflow tank by the battery.
If the over flow tank is overfilled then the coolant is then dumped via a tube onto the floor.
As the engine cools off, this creates a vacuum and the pressure cap allows the fluid to be drawn back into the system.
Phil
The excess coolant then gets transferred to the overflow tank by the battery.
If the over flow tank is overfilled then the coolant is then dumped via a tube onto the floor.
As the engine cools off, this creates a vacuum and the pressure cap allows the fluid to be drawn back into the system.
Phil
10 October 2008, 05:04 PM
#7
Yup dead right.
The excess coolant then gets transferred to the overflow tank by the battery.
If the over flow tank is overfilled then the coolant is then dumped via a tube onto the floor.
As the engine cools off, this creates a vacuum and the pressure cap allows the fluid to be drawn back into the system.
Phil
The excess coolant then gets transferred to the overflow tank by the battery.
If the over flow tank is overfilled then the coolant is then dumped via a tube onto the floor.
As the engine cools off, this creates a vacuum and the pressure cap allows the fluid to be drawn back into the system.
Phil
... Hence the theoretical phrase "lossless system", right 
Cheers turbotits (love that handle lol), also
. Good stuff, you two.
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