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Re: Pressure yes or pressure no? Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Thu, 29 Apr 2004 06:50:45
In Reply to: Pressure yes or pressure no?, david, Thu, 29 Apr 2004 05:53:20 Members do not see ads below this line. - Help Keep This Site Online - Signup |
The system is designed to run at pressure. The boiling point of liquids is higher at higher pressure - that's how pressure cookers work. So an unpressurized system will 'boil over' at a lower temp.
When the system heats up, the coolant expands, and flows into the expansion tank - hence the name. It should hold pressure.
In a normal, closed, pressurized system, when it heats up, you have pressurized air in the expansion tank. That's why removing it when warm is a bad, bad idea. Also, if the coolant is hot enough, the release of pressure drops the boiling point, and it can boil over just by opening the cap.
In that normal, closed, pressurized system, the hoses shouldn't be collapsed when cold - that indicates a vacuum formed. That tells me air escaped when the system was hot (and pressurized). When the system cooled down and things contracted, a vacuum was formed. This could happen two ways-
(1) when the system was hot, the cap was removed. This releases the pressurized air. The cap was put back on when the system was hot, but now it was at atmospheric pressure. When it cooled down and contracted, it dropped below atmospheric pressure, and the hoses collapsed. Simply venting the cap when cold will fix the issue.
(2) There is a small leak in the system. When hot and pressurized, the system vents pressure. When it cools down, the thing leaking contracts and seals itself before the body of the coolant cools, so the leak goes away. This is the same thing, effectively, as venting the cap when warm. The problem could be as simple as a slightly loose hose clamp.
posted by 192.249....
, Thu, 29 Apr 2004 08:54:31, Thu, 29 Apr 2004 06:50:45 <-- Viewing This Message
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