305E CR and 305.5E CR Mini Hydraulic Excavators Hydraulic System Caterpillar

Specification

Introduction

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

Required Tools

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".
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   Illustration 1	g02194183
   Pilot manifold (1) Pressure tap

4. Connect a 34,450 kPa (5,000 psi) pressure sensor to pressure tap (1).

Test Procedure

1. Start the engine.

2. Place the engine speed dial at the HIGH IDLE position. Refer to Testing and Adjusting, "Engine Performance - Test (Engine Speed)" for engine rpm settings.

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

4. Check the pilot relief valve setting at pressure tap (1).

5. The specification for the pilot relief valve setting is 3400 ± 200 kPa (493 ± 30 psi). If the pilot relief valve setting is not within the specification, adjust the pilot relief valve.

Adjustment Procedure

Illustration 2	g02194182
Pilot manifold (2) Pilot relief valve

Illustration 3	g02194181
Pilot manifold (2) Pilot relief valve (3) Shims

1. Adjust the number of shims (3) in order to adjust pilot relief valve (2). Adding shims increases the pressure. Removing shims decreases the pressure.

   Note: Normal operation of the engine and pumps are necessary for the pressure adjustment. If the results of the pressure adjustments are not correct, then the engine and the pump characteristic curve should be checked.