STEM ASSEM. (straight) 7S1074 - Caterpillar

Illustration 1 g02090157
Left Side of Machine (1) Return manifoldReturn manifold (1) is located under the machine, on the left side and behind the hydraulic tank. Case drain lines from the following components are connected to the return manifold: propel pump, axle motor, drum motor and vibratory pump. Oil from these lines is combined and oil is directed to the thermal bypass valve. This valve is located inside the return manifold.The thermal bypass valve contains a wax pellet. The wax pellet expands as the hydraulic oil temperature increases. As the wax expands, the bypass spool moves. The bypass spool controls the oil flow from the return manifold to the hydraulic tank. Oil that flows through this port bypasses the oil cooler.When the oil is cold, the oil flows directly to the tank from the return manifold. When the hydraulic oil temperature reaches 49° C (120.0° F), the wax in the thermal bypass valve begins to expand. This action causes the spool to begin to close the passage to port "R" of the manifold. When the oil temperature reaches 63° C (145.0° F), the bypass spool is fully closed. In this case, the passage from the manifold to the hydraulic tank is fully closed, and all the oil flow is sent to the oil cooler.