An engine cooling apparatus for a construction machine, the engine cooling apparatus comprising an expansion tank (30; 30A) performing, in a condition of being closed from an atmosphere, gas-liquid separation of coolant that circulates through the engine cooling apparatus, the expansion tank (30; 30A) comprising: a bulkhead; a first separate chamber group arranged as a first chamber that is constituted by separate chambers (R4 - R6; RA1 - RA6, RA10 - RA12, RA15, RA16, RA20 - RA25) separated from each other by the bulkhead; a second separate chamber group arranged as a second chamber that is constituted by separate chambers (R1 - R3; RA7 - RA9, RA13, RA14; RA17 - RA19) separated from each other by the bulkhead, the first and second chambers being also separated from each other by the bulkhead; an intake port formed in an outer wall of the expansion tank so as to open into the first separate chamber group, the intake port allowing coolant to be introduced into the expansion tank (30; 30A) from the engine cooling apparatus; a delivery port formed in the outer wall of the expansion tank so as to open into a chamber of the second separate chamber group at a lower position than a predetermined height, the delivery port allowing coolant to be delivered from the expansion tank (30; 30A) to the engine cooling apparatus; and a coolant supply port formed so as to open into the first separate chamber group at a higher position than the predetermined height, the coolant supply port allowing coolant to be supplied to the expansion tank in a condition of the expansion tank (30; 30A) being opened to the atmosphere, wherein the first and second separate chamber groups (X,Y) communicate with each other via a coolant communication hole, the coolant communication hole being formed at a lower position than the predetermined height in the bulkhead to allow coolant to circulate, and via an air communication hole, the air communication hole being formed at the predetermined height in the bulkhead, characterised in that the separate chambers (R4 - R6; RA1 - RA6, RA10 - RA12, RA15, RA16, RA20 - RA25) constituting the first separate chamber group communicate with one another via air communication holes that are formed in the bulkhead at a higher position than the predetermined height; the separate chambers (R1 - R3; RA7 - RA9, RA13, RA14, RA17 - RA19) constituting the second separate chamber group communicate with one another via air communication holes that are formed in the bulkhead at a higher position than the predetermined height and the predetermined height is set in accordance with an amount of air that can absorb pressure variations occurring with volume change of the coolant. a bulkhead; a first separate chamber group arranged as a first chamber that is constituted by separate chambers (R4 - R6; RA1 - RA6, RA10 - RA12, RA15, RA16, RA20 - RA25) separated from each other by the bulkhead; a second separate chamber group arranged as a second chamber that is constituted by separate chambers (R1 - R3; RA7 - RA9, RA13, RA14; RA17 - RA19) separated from each other by the bulkhead, the first and second chambers being also separated from each other by the bulkhead; an intake port formed in an outer wall of the expansion tank so as to open into the first separate chamber group, the intake port allowing coolant to be introduced into the expansion tank (30; 30A) from the engine cooling apparatus; a delivery port formed in the outer wall of the expansion tank so as to open into a chamber of the second separate chamber group at a lower position than a predetermined height, the delivery port allowing coolant to be delivered from the expansion tank (30; 30A) to the engine cooling apparatus; and a coolant supply port formed so as to open into the first separate chamber group at a higher position than the predetermined height, the coolant supply port allowing coolant to be supplied to the expansion tank in a condition of the expansion tank (30; 30A) being opened to the atmosphere, wherein the first and second separate chamber groups (X,Y) communicate with each other via a coolant communication hole, the coolant communication hole being formed at a lower position than the predetermined height in the bulkhead to allow coolant to circulate, and via an air communication hole, the air communication hole being formed at the predetermined height in the bulkhead, characterised in that the separate chambers (R4 - R6; RA1 - RA6, RA10 - RA12, RA15, RA16, RA20 - RA25) constituting the first separate chamber group communicate with one another via air communication holes that are formed in the bulkhead at a higher position than the predetermined height; the separate chambers (R1 - R3; RA7 - RA9, RA13, RA14, RA17 - RA19) constituting the second separate chamber group communicate with one another via air communication holes that are formed in the bulkhead at a higher position than the predetermined height and the predetermined height is set in accordance with an amount of air that can absorb pressure variations occurring with volume change of the coolant.