Oil cooler (100) for a vehicle, with: a supply tank (101) for the inflow of
working fluid; a
discharge tank (103) which is spaced apart from the inflow tank (101) by a predetermined distance and has a
discharge hole (104) on a side facing the inflow tank (101); a plurality of pipes (T) which connect the inlet tank (101) to the outlet tank (103) in a longitudinal direction for the flow of the
working fluid; a
bypass valve (110) integrally mounted on an outer side of an end section of the inlet tank (101) and connected to an inner side of the inlet tank (101) to divert
working fluid flowing therein by selectively opening and closing depending on the temperature of the working fluid or to direct it into the inlet tank (103); and a drain line (107) wherein one end is attached to the
discharge hole (104) and another end is attached to the
bypass valve (110) to connect the drain tank (103) to the
bypass valve (110) for the discharge of the working fluid in the drain tank (103) via the bypass valve (110) according to the actuation of the bypass valve (110), wherein the bypass valve (110) has: a valve housing (111) which is integrally attached to the outside of one end of the inlet tank (101) and projects from one side of the inlet tank (101); and a
control unit (120) which is arranged in the valve housing (111) and controls the working fluid to flow into or bypass the inlet tank (101) by performing an expansion or contraction depending on the temperature of the inflowing working fluid, wherein the valve housing (111) has: a first inlet hole (112) formed on one side of the same, which is the opposite end of the inlet tank (101), in order to attach an inlet connection (P1) to it; a bypass hole (114) formed on a further side of the same, which is spaced apart from the first inflow hole (112) in order to attach a bypass connection (P2) to it; a second inlet hole (113) facing the first inlet hole (112) at a surface that is in contact with the inlet tank (101) and connected to the inside of the inlet tank (101); and a connecting hole (115) spaced apart from the second inlet hole (113), with a protruding part extending from one side of the inlet tank (101) so that the other end of the drain
pipe (107) is connected to it, wherein the
control unit (120) has: a sliding element (121) in which one end is open and a mounting hole (H) is formed at the center of a further end, wherein a first opening hole (123) is formed on a side that corresponds to the first inlet hole (112) and the bypass hole (114) in a longitudinal direction, and at least a second opening hole (125) is formed on a further side that corresponds to the second inlet hole (113) and the connecting hole (115) in the longitudinal direction, and which is slidably inserted into the valve housing (111); an end cap (127) which is attached to a mounting hole (H) formed in the valve body to insert the sliding element (121) into the mounting hole (H), to close the mounting hole (H) and to form a mounting recess (129) at the center thereof; a fastening rod (135) with one end that is attached to the fastening recess (129); a deformable element (137) that is inserted into the sliding element (121) and moves forward or backward along the fastening rod (135) by expanding or contracting depending on the temperature of the working fluid in order to selectively move the sliding element (121) forward and backward; and a first elastic element (141) which is inserted between the valve housing (111) and the sliding element (121) and is compressed or stretched to provide an elastic force when the sliding element (121) moves, wherein the sliding element (121) has at least one relief hole (143) which is spaced apart from a mounting part (122) on the other side, where the mounting part (122) is formed, and which are spaced apart from each other at a predetermined angle in a circumferential direction around the mounting part (122).