TUBE 3578789 - 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.
The hydraulic oil tank is on the right side of the machine.
Illustration 1 g00368271
Park the machine on level ground. Position the boom as shown in illustration 1.
Illustration 2 g00567237
(A) High temperature range (B) Low temperature range
For a cold machine, maintain the hydraulic oil level in the low temperature range. For a machine that is at normal operating temperature, maintain the hydraulic oil level in the high temperature range.
Illustration 3 g00564984
Note: Refer to Operation and Maintenance Manual, "General Hazard Information" for information on containing fluid spillage.
Slowly loosen the fill/vent plug in order to relieve any pressure. Add oil, if necessary.
Check the O-ring seal of the fill/vent plug. Replace the O-ring seal if the O-ring seal is damaged.
Clean the fill/vent plug and install the fill/vent plug.