Oil Pump: Function

2014 Subaru Forester 2.5i, Eng CD FB25BA, Standard TransSECTION Function
WARNING: This page is about a different car, the 2013 Subaru Forester, 2012 Subaru Forester, 2011 Subaru Forester, and 2010 Subaru Forester. However, it is still accessible from the selected car via links, so may be relevant.
  • The pump draws automatic transmission fluid (ATF) from the oil pan through the oil strainer located under the control valve assembly. The ATF then flows through a passage in the transmission case, and after passing through the oil pump housing and oil pump cover, it enters the suction port.
  • As the inner rotor rotates, the outer rotor also rotates. This motion causes the ATF to be sucked up through the suction port and discharged from the discharge port.
  • The discharged ATF flows through a passage in the oil pump cover and then a passage in the oil pump housing. It then goes through a passage in the transmission case to the control valve assembly, from which the ATF is directed to various clutches, brakes, and torque converter lockup clutch for acting as hydraulic fluid and lubricating oil. Part of the ATF also flows to the manual valve, from where it is distributed to the circuit corresponding to the range selected by the selector lever.
  • As engine speed increases, the delivery rate of the oil pump also increases.
    Fig 1: Identifying Delivery Port, Oil Pump Housing, Outer And Inner Rotor, Suction Port, Oil Pan And Strainer
    G08260895Courtesy of SUBARU OF AMERICA, INC.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • β€’ You smell fuel, burning insulation, or see smoke.
  • β€’ Brakes feel soft, pull hard to one side, or make grinding noises.
  • β€’ The engine overheats, stalls repeatedly, or misfires under load.
  • β€’ You are missing required tools, torque specs, or safe lifting equipment.
  • β€’ You are not confident in the next step or safety outcome.