259D Skid Steer Loaders Machine Systems – Implement System – Test – Pressure

------ WARNING! ------

Personal injury or death can result from escaping fluid under pressure.

Escaping fluid under pressure, even a very small pin-hole size leak, can penetrate body tissue and cause serious injury and possible death. If fluid is injected into your skin, it must be treated immediately by a doctor familiar with this type of injury.

Always use a board or cardboard when checking for a leak.



Care must be taken to ensure that fluids are contained during performance of inspection, maintenance, testing, adjusting, and repair of the product. Be prepared to collect the fluid with suitable containers before opening any compartment or disassembling any component containing fluids.

Refer to Special Publication, NENG2500, "Dealer Service Tool Catalog" for tools and supplies suitable to collect and contain fluids on Cat products.

Dispose of all fluids according to local regulations and mandates.


Do not adjust the main relief valve above the specified pressure. Adjustment of the main relief valve above the specified pressure may cause damage to the gear pump.


Table 1
Main Relief Valve Specifications    
Description     Specification     Actual    
All Standard Flow Models    
23000 ± 700 kPa (3335 ± 102 psi)    
236D, 242D, 257D, 259D High Flow    
23000 ± 700 kPa (3335 ± 102 psi)    
All High Flow (XPS) and (XHP) Models    
23000 ± 1000 kPa (3335 ± 145 psi)    


The following test is performed in order to determine if the main relief valve for the work tool is damaged or improperly set.

Required Tools

Illustration 1g02571852

Tooling (A) 198-4240 Digital Pressure Indicator Gp

Illustration 2g02726620

Table 2
Tool     Item     Qty     Part No     Description    
A         198-4240     Digital Pressure Indicator Gp    
A     A1     1     198-4234     Digital Indicator    
A2 1     198-4239     Pressure Sensor Gp
(0 to 41,368 kPa (0 to 6,000 psi))    
A3 1     198-4236     Adapter Cable As    
B     B1     1     8T-08656     Pressure Gauge
(0 TO 6,000-KPA (0 TO 970-PSI))    
B2 1     6V-3989     Fitting    
B3 2     6V-4143     Quick Connect Coupler    
B4 1     177-7861     Hose As

4.3 m (14 ft)    

Test Preparation

Before any tests are performed, visually inspect the complete hydraulic system for oil leaks and damaged parts. Refer to Testing and Adjusting, "Visual Inspection". Before any tests are performed, prepare the machine for troubleshooting. Refer to Testing and Adjusting, "Machine Preparation for Troubleshooting".

Test Procedure

  1. Engage the parking brake. Stop the engine.

  1. Raise the cab. refer to Operation and Maintenance Manual, "Cab Tilting" for tilting procedure.

    Illustration 3g03410708

    Typical example of Standard Flow Valve

    (1) Load sensing relief valve

    (2) Pressure tap

    Illustration 4g03410759

    Illustration 5g03410716

    Typical example of High Flow Valve

    (1) Load sensing relief valve

    (2) Pressure tap

  1. Install either Tooling A or Tooling B to Pressure tap (2) .

  1. Lower cab. Secure the hydraulic line so that the pressure gauge can be viewed by the operator during test. Make sure that the hoses are not pinched when the cab is lowered.

  1. Sit in the operator seat. Fasten the seat belt. Lower the armrest. Disengage the parking brake.

    Note: The oil in the hydraulic system must be at an operating temperature of 50° ± 10°C (122° ± 18°F). This temperature range is specified for standard factory fill oil only. Use the Electronic Technician Software in order to monitor this temperature. Or refer to Testing and Adjusting, "Hydraulic Oil Temperature Test" for an alternate procedure.

  1. Run the engine at HIGH IDLE.

    Note: Do not stall the hydraulic system for more than 10 seconds. If necessary, release the work tool from the stall condition. After 30 seconds have passed, repeat Step 7.

  1. With no work tool high flow work tool connected the machine roll the right-hand thumb wheel above 80%, record pressure.

  1. If the pressure reading is within specifications, proceed to step10. Refer to table 1

  1. If pressure reading is not within specifications, refer to the section titled "Hydraulic Troubleshooting" in this manual.

  1. Release the hydraulic system pressure. Refer to Testing and Adjusting, "Hydraulic System Pressure Release" for the proper procedure.

  1. Raise the cab and remove Tooling (A). Refer to Operation and Maintenance Manual, "Cab Tilting".

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