Komatsu PC138USLC Operation & Maintenance Manual page 339

MAINTENANCE PROCEDURE MAINTENANCE PROCEDURE
5. Set the oil container under the drain plug under the machine.
Using the handle, remove drain plug (P) and drain the oil.
Check the O-ring installed to plug (P), and if it is dam-aged,
replace the O-ring. After draining the oil, tighten drain plug (P).
Tightening torque: 58.8-78.4 Nm (6-8 kgm, 43.4-57.9 lbft).
Take care not to get oil on yourself when you remove drain
plug (P).
6. Add the replacement amount of oil through oil filler (F). Check that the oil level is between the H and L lines on
the sight gauge.
For details of oil level check, see "Check Oil Level in Hydraulic Tank, Add Oil (PAGE 3-119)".
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MAINTENANCE MAINTENANCE