170° is a pretty low operating temp . Most cars actually run closer to 200 ° .
A coolant recovery system is not just a bottle with a hole drilled in it. It also has a special radiator cap that operates as a 2 way valve to allow hot coolant to escape into the bottle and then to flow back into the radiator as it cools down.
This eliminates air in the radiator helping to keep corrosion and temps lower in the cooling system.
Just a bottle to capture the coolant as the coolant expands in the radiator without a backflowing cap would require constant "topping off" of the coolant.
Most post 1973 automobiles came equipped with the recovery system.
