Quote:
Originally Posted by redvtech07
well there is more to it than that. When the car is cool there will be less coolant in the overflow tank.... when the car is hot there will be more coolant in the overflow tank. This is because as the liquid gets hot and cool it expands and contracts
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I was responding to:
Quote:
Originally Posted by vtaaakkk!!
what i did when i put coolant in was fill it up slowly till it gets near the top and when it does leave it for a few minutes to let it settle then top it off. our cars have an overflow tank so if you think you put too much check it.
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You can't really overfill the radiator. Once the coolant level reaches the bottom of the filler neck, the radiator is essentially full. However, the cooling system must be purged of air. This can only be accomplished when the thermostat is open (cooling fans have cycled twice). After the thermostat is open, then you add more coolant until it reaches the bottom of the filler neck.
Now, coolant only flows into the coolant overflow reservoir when the cooling system pressure exceeds the pressure on the radiator cap. That is because there are two valves inside the radiator cap: a pressure and a vacuum valve.
Once the pressure exceeds approximately 13-15 psi, the pressure valve opens and coolant flows into the colant overflow reservoir. That is why the coolant should be no higher than the "MAX" line or between "MIN" and "MAX." If there is too much coolant in the overflow reservoir, the coolant may overflow when/ if coolant flows into the reservoir.
Next, when the vehicle is turned off and the temperature of the cooling system decreases, so too does the pressure in the cooling system. As the pressure decreases, a vacuum is created, causing the vacuum valve to open and the coolant inside the overflow reservoir is pulled back into the cooling system. If there is no coolant inside the overflow reservoir, this vacuum would suck in air. An excess of air inside the cooling system will cause the engine to overheat because the air is a poor coolant compared to the ethylene glycol/ water mixture. Air can also block coolant flow through the cooling passages if the air bubble is large enough.
Anyway, my point was that you cannot determine if you overfilled the radiator by looking at the overflow reservoir with the vehicle off. The car must be purged of air (thermostat open) and only after the car has cooled back down should you add coolant to the overflow reservoir (up to the "MAX" line).