Engine is overheating. it could also just be that your radiator cap is bad and allowing the pressure to release too soon. Keep an eye on your temperature gage, if is showing hot or over heated then check coolant level and possibly water pump problem or head gasket, if not overly hot then suspect the radiator cap.
The overflow tank for coolant will "boil" if there is air getting in the coolant chamber. This can be a head gasket going bad.
Coolant is old.
The overflow tank is either cracked or its overheating and leaking from the cap
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An overflow tank is a bottle that holds coolant that expands and leaves the radiator under driving conditions. The Coolant will go back into the radiator as needed.
in the overflow tank
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It means that you have a coolant leak. You need to have the system pressure tested for leaks.
Its either in the coolant overflow tank or in the side of the radiator
Add it in the overflow tank up to the max line.
Usually a blown head gasket.
Near the bottom of the coolant reservoir ( overflow tank)