An expansion tank intended to be included in a cooling system of a motor vehicle in order to receive coolant which circulates in the cooling system, the expansion tank comprising: - an outer casing; - an expansion chamber enclosed within the casing, wherein the expansion chamber comprises a lower part, in which coolant is to be accumulated, and an upper part, in which air is to be accumulated; - an inlet opening, here denominated first inlet opening, which is arranged in the casing and intended to be connected to a vent conduit of said cooling system in order to allow coolant and air to flow into said upper part of the expansion chamber via this first inlet opening; and - an outlet opening which is arranged in the casing and intended to be connected to a coolant conduit of said cooling system in order to allow coolant to flow out of said lower part of the expansion chamber via this outlet opening; wherein: - an inlet basin, here denominated first inlet basin, is arranged in said upper part of the expansion chamber, wherein this inlet basin is configured to receive the coolant which flows into the expansion chamber via said first inlet opening; - a settling basin is arranged in said upper part of the expansion chamber; - the first inlet basin is connected to the settling basin by a flow passage, via which coolant may flow from an upper part of the first inlet basin and down into the settling basin, wherein particulate contaminants contained in the coolant received in the settling basin is allowed to settle at the bottom of the settling basin under the effect of gravity; - the settling basin is provided with an outlet, via which coolant may flow from an upper part of settling basin and further on towards said lower part of the expansion chamber, characterized in that a second inlet opening is arranged in the casing and intended to be connected to a vent conduit of said cooling system in order to allow coolant and air to flow into the expansion chamber via this second inlet opening, wherein the expansion tank is so configured that the coolant entering the expansion chamber via the second inlet opening is allowed to flow to said lower part of the expansion chamber without passing the first inlet basin and the settling basin. - an outer casing; - an expansion chamber enclosed within the casing, wherein the expansion chamber comprises a lower part, in which coolant is to be accumulated, and an upper part, in which air is to be accumulated; - an inlet opening, here denominated first inlet opening, which is arranged in the casing and intended to be connected to a vent conduit of said cooling system in order to allow coolant and air to flow into said upper part of the expansion chamber via this first inlet opening; and - an outlet opening which is arranged in the casing and intended to be connected to a coolant conduit of said cooling system in order to allow coolant to flow out of said lower part of the expansion chamber via this outlet opening; wherein: - an inlet basin, here denominated first inlet basin, is arranged in said upper part of the expansion chamber, wherein this inlet basin is configured to receive the coolant which flows into the expansion chamber via said first inlet opening; - a settling basin is arranged in said upper part of the expansion chamber; - the first inlet basin is connected to the settling basin by a flow passage, via which coolant may flow from an upper part of the first inlet basin and down into the settling basin, wherein particulate contaminants contained in the coolant received in the settling basin is allowed to settle at the bottom of the settling basin under the effect of gravity; - the settling basin is provided with an outlet, via which coolant may flow from an upper part of settling basin and further on towards said lower part of the expansion chamber,