The invention relates to a tank used in an engine cooling system, the engine cooling system, and a work machine. The tank includes a housing and a partition which dividing the housing into an exhaust tank and an expansion tank which are sealed from each other. The exhaust tank includes a first connecting pipe and a second connecting pipe, the first connecting pipe being adapted to be fluidly connected to an engine cylinder jacket of the engine cooling system to introduce coolant into the exhaust tank, and the second connecting pipe being adapted to be fluidly connected to a heat exchanger of the engine cooling system to discharge the coolant into the heat exchanger. The expansion tank includes a third connecting pipe adapted to be fluidly connected to the engine cooling system. The tank further includes a guiding tube having a first end in communication with the exhaust tank, and a second end arranged in the expansion tank, so that gas contained in the coolant flowing through the exhaust tank is exported into the expansion tank through the guiding tube. The exhaust tank enables the gas in the coolant to be separated before entering the heat exchanger, and the thermal stress impact to the heat exchanger is reduced.