MoparLeo said

If you want the system to work like a normal recovery system, you need a different type of cap. A regular cap only vents coolant out. S ecovery cap has a 2 way valve. When the radiator heats up and the colant xpands, it lets coolant drain to the bottle. When the system cools down, a sligh vaccum occurs in the cooling system and the cap will open again to let coolant from the bottle go back into the radiator.

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