PIN 2399940 - Caterpillar

Never remove the fill/vent plug from the hydraulic tank if the oil is hot.Air can enter the system and cause pump damage.
Park the machine in the servicing position on level ground.
Illustration 1 g03447317
(A) High temperature range
(B) Low temperature range
For a machine that is at normal operating temperature, maintain the hydraulic oil level in the high temperature range. For a cold machine, maintain the hydraulic oil level in the low temperature range. Note: Refer to Operation and Maintenance Manual, "General Hazard Information" for information on containing fluid spillage.
The Hydraulic fill cap is located on top of the Hydraulic tank.
Illustration 2 g02024028
Pressurized system!The hydraulic tank contains hot oil under pressure. To prevent burns from the sudden release of hot oil, relieve the tank pressure with the engine off by slowly turning the cap approximately 1/8 of a turn until the cap reaches the secondary stop.
Illustration 3 g02275615
Filler cap
(A) LOCK position
(B) PRESSURE RELEASE - START position
(C) PRESSURE RELEASE - END position
(D) OPEN position
Release the pressure that may be present in the return hydraulic circuit with the following procedure. Refer to Illustration 3 for filler cap positions.
Turn the filler cap counterclockwise, with no downward force applied, and move the arrow from position (A) to position (B).
Release the pressure for a minimum of 45 seconds by moving the arrow from position (B) to position (C).
Push the center of the filler cap down. Without tilting the filler cap, move the arrow from position (C) to position (D).
The hydraulic tank pressure is relieved. The filler cap can now be removed if needed.
Tighten the filler cap on the hydraulic tank to position (A).
After the pressure is relieved, tighten the filler cap.