SEAL 3978039 - Caterpillar

Removal Procedure
Table 1
Required Tools    
Tool     Part Number     Part Description     Qty    
A     311-1362     Vacuum Gauge Gp     1    Start By:
Release the hydraulic system pressure.
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 removing any components or lines. Remove the oil filler cap only when the engine is stopped, and the filler cap is cool enough to touch with your bare hand.
Illustration 1 g02544519
Remove the cap from the hydraulic tank. Install Tooling (A) onto the hydraulic tank. Attach an air supply hose to Tooling (A). Apply 276 to 414 kPa (40 to 60 psi) of air. This procedure will pull vacuum on the hydraulic system.
Illustration 2 g02240674
Remove cover assembly (1) .
Illustration 3 g02240336
Disconnect hose assemblies (4). Remove bolts (5) .
Remove bolts (2) and load control valve (boom cylinder) (3) .Installation Procedure
Install load control valve (boom cylinder) (3) in the reverse order of removal.
Check the hydraulic oil level. Refer to, "Hydraulic System Oil Level - Check".