259D Skid Steer Loaders Machine Systems – Main Relief Valve – Adjust

------ 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.


The following adjustment procedure is used to se main relief valve pressure.

Procedure Preparation

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

Main Relief Valve Adjustment

  1. Engage the parking brake. Stop the engine.

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

    Illustration 1g03410708

    Typical example of work tool valve on the 236D 242D 257D and 259D models.

    (1) Main relief valve

    (2) Pressure tap

  1. Locate the main relief valve (1) .

    Illustration 2g03412419

  1. Loosen the locknut (3). turn adjustment (4) clockwise in order to in crease the relief valve pressure. Turn the adjustment screw (4) counterclockwise in order to reduce relief valve pressure.

  1. Tighten locknut (3) to a torque of 18 ± 2 N·m (13 ± 1.5 lb ft).

  1. Lower the cab and perform the test procedure in Testing and Adjusting, "Implement System - Test (Pressure)".

  1. If pressure in with in specifications refer to step 9

  1. If pressure is not with in specifications, repeat this procedure.

  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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