GRADIENT-TYPE EXPANSION TANK FOR AUTOMOBILE

A step-type vehicle expansion water tank includes a water-tank body (8), an interior of the water-tank body (8) is separated by two water separating plates (4) of different heights into a higher chamber (9), a middle chamber (10) and a lower chamber (11), the chambers have tops that are communicated and bottoms that are individually provided with a water outlet (5), and a filling port (1) that corresponds to the higher chamber (9) is provided at the top of the water-tank body (8). The step-type vehicle expansion water tank, by using the step-type structure, can integrate the filling processes of the cooling systems for the engine, for the electric motor and for the power battery. The step-type structure realizes the water blocking between the areas, and, by using the water blocking plates (3) and the water separating plates (4), even if the vehicle is running on a steep slope, the mutual mixing of the waters can be prevented. When the vehicle has recovered to run on an even road surface, the waters of the independent systems quickly recover.