CONT GP 1187631 - Caterpillar

Personal injury can result from hydraulic oil pressure and hot oil.Hydraulic oil pressure can remain in the hydraulic system after the engine has been stopped. Serious injury can be caused if this pressure is not released before any service is done on the hydraulic system.Make sure all of the work tools have been lowered to the ground, and the oil is cool before performing any service. Remove the oil filler cap only when the engine is stopped, and the filler cap is cool enough to touch with your bare hand.
The release of hydraulic pressure in a hydraulic circuit is required before service is performed to that hydraulic circuit. Release the pressure in the hydraulic circuits before any hydraulic lines are disconnected or removed from that hydraulic circuit.Reference: Refer to the Operation and Maintenance Manual, "System Pressure Release" for the detailed procedure to release the system pressure.