COVER 0398505 - Caterpillar

Introduction
This special Instruction covers the field installation of a back pressure valve in the return line on Medium Wheel Loader machines. This installation will eliminate voiding of the lift cylinder and tilt cylinder that can be encountered during back dragging or grading applications.Do not perform any procedure or order any parts outlined in this publication until you understand the information that is contained in this document.
Sudden movement or accidental starting of the machine can cause personal injury or death to persons on or near the machine.To prevent personal injury or death, perform the following:Park the machine on a smooth level surface.Lower the bucket and or attachments to the ground.Stop the engine and engage the parking brake.Block the wheels and install the steering frame lock.Turn the battery disconnect switch to the OFF position and remove the key.Place a Special Instruction, SEHS7332, "Do Not Operate" tag at the battery disconnect switch location to inform personnel that the machine is being worked on.
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.
Required Parts
Table 1
Quantity     Part Number     Description     Usage    
1     353-7179     Check Valve Gp        
1     356-6755     Hose As     950H/962H/IT62H with Steering Wheel (HMU)    
1     356-6758     Hose As     950H/962H/IT62H with Command Control Steering (CCS)    
1     356-6759     Hose As     966H/972H with Steering Wheel (HMU)    
1     356-6760     Hose As     966H/972H with Command Control Steering (CCS)    
3     4J-0524     O-Ring Seals        
4     7X-2550     Bolts        Note: Installation requires one back pressure valve, two seals, four bolts, and one of the four hoses in Table 1. Use the appropriate hose for the model and for the steering system on the machine.Removal of Existing Return Hose
Illustration 1 g02074353
(1) Existing Return Hose
Remove existing return hose (1). Refer to Illustration 1.Note: The flanges from both sides of the hose will be reused. The bolts from the tank side of the hose will be reused.Installation of New Return Hose and Back Pressure Valve
Illustration 2 g02074554
Illustration 3 g02203155
Install the tank side of the new return hose with a new 4J-0524 O-Ring Seals . Reuse the existing flanges and the existing bolts.
Install main valve side of the new return hose with the 353-7179 Check Valve Gp and with new 4J-0524 O-Ring Seals and new 7X-2550 Bolts . Reuse the existing flanges.Note: Modify the bracket as needed. Refer to Illustration 3.