303.5E2 CR, 304E2 CR, 304.5E2 XTC, 305E2 CR and 305.5E2 CR Mini Hydraulic Excavators Hydraulic System Relief Valve (Pilot) - Test and Adjust Caterpillar


Relief Valve (Pilot) - Test and Adjust
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303.5E2 CR, 304E2 CR, 304.5E2 XTC, 305E2 CR and 305.5E2 CR Mini Hydraulic Excavators Hydraulic System [UENR4294]
HYDRAULIC SYSTEM
VALVE GP-PILOT RELIEF
303.5E2 CR, 304E2 CR, 304.5E2 XTC, 305E2 CR and 305.5E2 CR Mini Hydraulic Excavators Hydraulic System Relief Valve (Pilot) - Test and Adjust
303.5E2 CR, 304E2 CR, 304.5E2 XTC, 305E2 CR and 305.5E2 CR Mini Hydraulic Excavators Hydraulic System Relief Valve (Pilot) - Test and Adjust
1.1. Specification
2.1. Introduction
3.1. Required Tools
4.1. Machine Preparation
5.1. Test Procedure
6.1. Adjustment Procedure

Specification

Table 1
Pilot Relief Valve Pressure Setting 
Machine Settings  Engine Speed 
Engine Speed Dial "High Idle"
Item  Specification  Actual 
Pilot relief valve  4100 ± 200 kPa
(595 ± 30 psi) 
 

Introduction

The pilot relief valve limits the pressure in the pilot system. The pilot relief valve setting is adjustable.

Required Tools

Table 2
Required Tools 
Part Number  Description  Qty 
198-4240  Digital Pressure Indicator Gp   
198-4234  Digital Indicator 
198-4238  Pressure Sensor Gp 
198-4236  Adapter Cable As 

Machine Preparation

  1. Place the machine on level ground.

  2. Stop the engine.

  3. Release the pressure in the hydraulic system. Refer to Testing and Adjusting, "Hydraulic System Pressure - Release".


    Illustration 1g06032321
    Main control valve
    (1) Pressure tap
    (2) Jam nut
    (3) Pressure reducing valve

  4. Connect a 34450 kPa (5000 psi) pressure gauge to pressure tap (1).

Test Procedure

  1. Start the engine.

  2. Place the machine controls at the following settings: engine speed dial "High Idle". Refer to Testing and Adjusting, "Engine Performance - Test (Engine Speed)" for engine rpm settings.

  3. Place the hydraulic activation control lever in the UNLOCKED position.

  4. Increase the hydraulic oil temperature to 55° ± 5°C (131° ± 9°F).

  5. Stall any implement function and check the pilot pressure setting at pressure tap (1).

  6. The pilot pressure setting should be 4100 ± 200 kPa (594.7 ± 29.0 psi). If the pilot pressure setting is not within the specification, adjust pressure reducing valve (3).

Adjustment Procedure



    Illustration 2g06032327
    Main control valve
    (2) Jam nut
    (3) Pressure reducing valve

  1. Remove cap from pressure reducing valve (3) to expose the internal hex screw.

  2. In order to adjust pressure reducing valve (3), loosen jam nut (2).

  3. Turn the internal hex screw until the pressure gauge reading at pressure tap (1) is 4100 ± 200 kPa (595 ± 29.0 psi).

    Note: Turn the internal hex screw clockwise to increase the pressure. Turn the internal hex screw counterclockwise to decrease the pressure.

    Note: Always make final pressure adjustments on pressure increase.

  4. Tighten jam nut (2) to a torque of 8.1 ± 1.3 N·m (6.0 ± 1.0 lb ft).

  5. Repeat the"Test Procedure" to confirm the pressure setting.

  6. Replace the cap on pressure reducing valve (3).

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