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Cooling system capacities

Do the cooling system capacities given in owner’s manual normally include the plastic
overflow reservoir in the total capacity?

No, it does not

.I don’t think total capacity includes the overflow reservoir

Definitely not! The “overflow” is to contain the fluid as it expands, and to make sure there is enough to be sucked back into the system when a small loss occurs.

I first encountered these overflow tank in military vehicles in the 50s, and thought it was a great idea!.

I thought that’s what I said. It’s a yes or no question.

I believe the capacity includes up to the co;d line on the tank.

At any rate I’ve never been able to get that much in the cooling system anyway but never pulled the plugs on the block.

There were some vehicles in the recent past that had dual chambers in the coolant reservoir, the main chamber is the reservoir and the second chamber the overflow to prevent coolant from spilling onto the road during high temperature operation. You cannot add fluid to the over flow chamber, it is sealed.

That is the exception, most vehicles have only a coolant reservoir and no “over flow” container. The fluid needed to refill the cooling system and reservoir is the cooling system capacity specifications.

So we have a disagreement between the early replies and the late replies.

Could be the difference between what is referred to as an “over flow tank” versus the tank that is actually part of the cooling system. If there is no radiator cap, coolant is added to the reservoir which I assume is considered an extension of the radiator. If there is a radiator cap, then I believe the tank would be considered an over-flow tank and not part of the coolant capacity. Even though the tank also provides the function of an over-flow. So as usual everyone is correct and there is no easy yes or no answer. But why do you ask?

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An over-flow tank or “catch can” is used to prevent spills and can be left empty.

A reservoir (non pressurized) generally holds between a pint and 2 quarts depending on cooling system size, it has a normal fill range. You need to have enough coolant to refill the entire cooling system, that value is listed as the cooling system capacity.


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