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you haven't read my post have you, the statement that the cap opens because of temperature is incorrect, it is pressure.
go and read my post then go and do it.
there are three basic systems that are, have been used on liquid cooling systems on motor cars.
1. radiator and nothing else, when the engine gets hot it expells the increase in volume through a cap, either pressurized or not, to atmosphire.
2. as above but not to atmosphire but to a resovoir which is open to atmophire via a hose to the bottom of the resovoir allowing the resovoir to catch the expelled coolant, when the system cools down, the radiator coolant decreases in volume and creates a vacuum in the radiator, because of the design of the radiator cap the water is sucked back into the radiator from the cooling tank by the created vacuum, the radiator cap prevents the vacuum from drawing air in instead of the previously expelled coolant.
3. a completely pressurized system, this is nothing like the syetem described in "2". in that due to the unrelyable radiator cap seals and considerable loss of vacuum in the system , it was deemed better to just have a larger volume system in the first place.
this is a much better system as nothing is generally expelled to atmosphire but contained in the system at all times unless repairs are needed.
it comprizes of a normal cooling system as described in 2, but instead of the pressure cap being fitted to the radiator, it required an expansion tank, this is the same as in 2 but is connected directly to the main cooling system instead of via the cap, this allows coolant to enter and leave the expansion tank as the temperature rises and falls, thus expanding and contracting, the coolant is kept at a pressure to increase the boiling point above 212/100 degrees dependant upon the rating of the cap which is now located on the expansion tank, therefore the expansion tank must be located above any other part of the system to ensure complete filling and evacuation of air or steam trapped in the cooling system via a vent pipe from the highest point in the system to the top of the expansion tank.
this system should not require any additional overflow resovoir as when completely filled at hot, that is the maximum volume of the system unless there is a fault in the cooling mechagnism, be it too small of an expansion volume or overall volume through poor design, faulty electric or mechanical fans, defective pressure cap or a leaking head gasket.
this system is in essence the same as system 1, and although it looks more complex, it is just designed to accomodate the lower body styles in modern vehicles with crossflow radiators and no top tank, years ago, the expansion tank would have been just an increase in the volume of the radiator header tank, that is all that is going on with an expansion tank system, and in old cars, the radiator top was generally higher than the rest of the cooling system.
as a point of interest, if your vehicle has system 2, and when cool, there is still the expelled coolant in the resovoir, then you have either a defective cap, a leak in the system or a leaking head gasket, it will expell the coolant into the resovoir when hot, but is not sufficiently hermetically sealed to maintain a vacuum when cooling down to draw the coolant back past the cap into the cooling system.
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this story shall the good man teach his son,
and chrispin chrispian shall ne'er go by,
from this day to the end of the world.
but we in it shall be remembered.
Last edited by john hennessy on November 25, 2014, 2:04 pm, edited 1 time in total.
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So anyway Mjalaly, there is this little red "!" to report offensive and moronic statements.......
