305 CR Mini Hydraulic Excavator Hydraulic System Relief Valve (Line) - Test and Adjust Caterpillar


Relief Valve (Line) - Test and Adjust
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1.1. Test Procedure
2.1. Adjustment Procedure

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

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 attachments have been lowered, 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.

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

Do not check for leaks with your hands. Pin hole (very small) leaks can result in a high velocity oil stream that will be invisible close to the hose. This oil can penetrate the skin and cause personal injury. Use cardboard or paper to locate pin hole leaks.

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NOTICE

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, "AVSpare Tools and Shop Products Guide" for tools and supplies suitable to collect and contain fluids on AVSpare products.

Dispose of all fluids according to local regulations and mandates.


Test Procedure

Table 1
Required Tools    
Part Number     Description     Quantity    
8T-0860     Pressure Gauge     2    
6V-3014     Hose     2    
6V-4143     Coupler Assembly     4    

Before you perform these procedures, refer to Testing and Adjusting, "Machine Preparation" for the proper procedure to prepare the machine.

Note: The following tests require operating the engine at high idle. Refer to Testing and Adjusting, "Engine Performance - Test".

Note: A temporary setting of the main relief valve is required before any line relief valve can be tested. Temporarily adjust main relief valve (P1) in order to test the boom line relief valves and the bucket line relief valve. Temporarily adjust main relief valve (P2) in order to test the stick line relief valves. Refer to Testing and Adjusting, "Relief Valve (Main) - Test and Adjust".

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



    Illustration 1g00836560

    Engine compartment

    (1) Pressure tap (P1)

    (2) Pressure tap (P2)

    (3) Pressure tap (P3)

  1. Open the engine hood in order to access the pressure taps for the main relief valves.

  1. Connect a 40000 kPa (5800 psi) pressure gauge to pressure tap (1) .

  1. Connect a 40000 kPa (5800 psi) pressure gauge to pressure tap (2) .

  1. Start the engine. Be sure that the engine is at high idle.

  1. Move the bucket's control lever to the CLOSE position and hold. Make a note of the reading on the gauge attached to pressure tap (1) .

  1. The pressure should be 27900 ± 1500 kPa (4050 ± 220 psi).

  1. Move the boom's control lever forward to the LOWER position and hold. Make a note of the reading on the gauge attached to the pressure tap (1) .

  1. The pressure should be 27900 ± 1500 kPa (4050 ± 220 psi).

  1. Move the stick's control lever forward to the OUT position and hold. Make a note of the reading on the gauge attached to pressure tap (2) .

  1. The pressure should be 27900 ± 1500 kPa (4050 ± 220 psi).

  1. Move the stick's control lever backward to the IN position and hold. Make a note of the reading on the gauge attached to the pressure tap (2) .

  1. The pressure should be 27900 ± 1500 kPa (4050 ± 220 psi).

  1. If any of the pressure readings are not set to the correct specifications, adjustment of that line relief valve is necessary. Refer to the "Adjustment Procedure".

Adjustment Procedure




    Illustration 2g00837781

    Top view of main control valve

    (4) Line relief valve (bucket cylinder head end)

    (5) Line relief valve (boom cylinder rod end)

    (6) Line relief valve (boom head)

    (7) Line relief valve (stick cylinder head end)

    (8) Line relief valve (stick cylinder rod end)

  1. The following line relief valves are located on the right side of the main control valve: (4) bucket cylinder head end, (5) boom cylinder rod end, (6) boom head and (7) stick cylinder head end. Line relief valve (8) for the stick cylinder rod end is located on the left side of the main control valve.



    Illustration 3g00343372

    Line relief valve (typical example)

    (14) Locknut

    (15) Adjustment screw

  1. Determine the line relief valves that require adjustment. Loosen locknut (14). Turn adjustment screw (15) in order to adjust the pressure. Turning adjustment screw (15) clockwise increases the pressure. Turning adjustment screw (15) counterclockwise decreases the pressure. Tighten locknut (14) .

    Note: Always make final pressure adjustment on pressure rise.

    Note: Adjust the main relief valve to the specifications. Refer to Testing and Adjusting, "Relief Valve (Main) - Test and Adjust".

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