Chapter 5
Hydraulic System
Table of Contents
General Information..................................................................................................................................... 5–2
4520 Operator’s Manual and Accessory Installation Instructions ................................................ 5–2
Towing the 4520 ....................................................................................................................................... 5–2
Relieving Pressure from the Hydraulic System ................................................................................ 5–2
Remote Filtering the Hydraulic System .............................................................................................. 5–3
Testing the Static Implement Pressure ............................................................................................... 5–5
Testing the Hydrostatic Drive System Under Load .......................................................................... 5–5
Testing the Steering Valve P-Port Bypass ......................................................................................... 5–6
Adjusting the Hydraulic Pump Tow Valve........................................................................................... 5–7
Hydraulic Hoses ........................................................................................................................................... 5–9
Installing the Hydraulic Hoses and Tubes (O-Ring Face Seal)................................................... 5–10
Installing the Hydraulic Fittings (SAE Straight Thread O-Ring Fittings).................................... 5–12
Hydraulic Schematic ................................................................................................................................. 5–16
Hydraulic Flow Diagrams ......................................................................................................................... 5–17
Drive Circuit............................................................................................................................................. 5–17
Implement Circuit ................................................................................................................................... 5–18
Service and Repairs .................................................................................................................................. 5–19
General Precautions for Removing and Installing Hydraulic System Components............... 5–19
Removing the Front Hydraulic Motor ................................................................................................ 5–21
Installing the Front Hydraulic Motor................................................................................................... 5–22
Removing the Rear Hydraulic Motor ................................................................................................. 5–22
Installing the Rear Hydraulic Motor.................................................................................................... 5–23
Removing the Hydraulic Pump ........................................................................................................... 5–24
Installing the Hydraulic Pump ............................................................................................................. 5–26
Removing the SDLA Spool Valve....................................................................................................... 5–26
Installing the SDLA Spool Valve ......................................................................................................... 5–27
Replacing the SDLA Spool Valve Float Detent............................................................................... 5–28
Removing and Installing the Hydraulic Cooler Fan........................................................................ 5–29
Removing and Installing the Steering Valve.................................................................................... 5–30
Removing the Steering Cylinder......................................................................................................... 5–31
Installing the Steering Cylinder........................................................................................................... 5–32
Removing the Lift Cylinder................................................................................................................... 5–33
Installing the Lift Cylinder ..................................................................................................................... 5–34
Removing the 3–Point Hitch Spool Valve......................................................................................... 5–34
Installing the 3–Point Hitch Spool Valve ........................................................................................... 5–35
Removing the 3–Point Hitch Lift Cylinder......................................................................................... 5–36
Installing the 3–Point Hitch Lift Cylinder ........................................................................................... 5–37
Removing and Installing the Hydraulic Fluid Reservoir ................................................................ 5–37
4520P Page 5–1 Hydraulic System
09.40003Rev 00
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