PUMP GP-GEAR 2974661 - Caterpillar

Machine without a Boom Lowering Control Valve
Be sure no one is under or near the work tools before manually lowering the boom. Keep all personnel away from the boom drop area when lowering the boom with the engine stopped in order to avoid possible personal injury.
When you must manually lower the boom due to engine shutdown, use the following procedure.Relieve the pressure in the hydraulic system before manually lowering the boom. Move the hydraulic lockout lever to the UNLOCKED position. Move the travel levers/pedals forward and backward in order to relieve the pressure.
Illustration 1 g01220939
(1) Fill/vent plug
Slowly loosen fill/vent plug (1) on the top of the hydraulic tank until internal pressure in the hydraulic tank has been relieved. Remove fill/vent plug (1).
Open the engine hood.
Illustration 2 g01317035
(2) Hose
(3) Clamp
Loosen clamp (3) and disconnect hose (2) from the radiator.
Illustration 3 g01220942
(2) Hose
(4) Screw
Connect an end of hose (2) to screw (4). Put the other end of hose (2) into the filler plug opening.
Slowly loosen screw (4) by a maximum of 1/2 turn. This allows the hydraulic oil in the boom circuit to drain into the hydraulic tank. The boom will now start to lower.
Make sure that the work tool has lowered all the way to the ground. Tighten screw (4) to a torque of 13 2 N m (9 1 lb ft).
Disconnect hose (2) from screw (4). Do not allow the oil that is contained in hose (5) to spill. Drain the oil into a suitable container.
Connect hose (2) to the original position on the radiator and install fill/vent plug (1) securely.
Close the engine hood. After completion of the manual boom lowering, make necessary repairs before you operate the machine again.Machine with a Boom Lowering Control Valve
Boom load may cause cylinder oil pressure to reach relief pressure of the boom lowering control device when the boom is supported by one cylinder. Boom can lower suddenly, causing possible injury or death.To avoid possible injury or death, be sure no one is under or near the work tool before manually lowering the boom.Keep all personnel away from the boom drop area when lowering the boom with the engine stopped.
If the engine is shut down or the hydraulic system is disabled, the operator can still lower the boom. Use the following procedure if the machine is equipped with a boom lowering control valve.
Illustration 4 g01221008
(5) Locknut
(6) Check valve The boom lowering control valve (if equipped) is installed on each of the boom cylinders. The boom lowering control valve allows the operator to lower the boom if the engine is stopped. The boom lowering control valve also prevents the sudden descent of the boom if there is an oil leak in the hydraulic line of the boom.
Loosen locknut (5) of the boom lowering check valve.
Slowly turn check valve (6) counterclockwise until the check valve stops. The boom will lower to the ground.
Make sure that the work tool has been lowered onto the ground. Tighten check valve (6).
Tighten locknut (5) to a torque of 2.25