301.4C Mini Hydraulic Excavator Caterpillar

Introduction

The pilot relief valve is located on the pilot oil supply manifold on the right side of the machine. The pilot relief valve limits the pressure in the pilot system. The pilot relief valve setting is adjustable.

The pressure tap to measure the relief valve setting is located on the left side of the machine.

Required Tools

Illustration 1	g01623868
Tooling group "B" 198-4240 Digital Pressure Indicator Gp

Illustration 2	g03395931
Adapter assembly "C" (C1) Hose assembly (C2) Adapter assembly (C3) Fitting

Machine Preparation

1. Position 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".
   Show/hide table

   Illustration 3	g02646809
   Pressure tap for the pilot system pressure located on the left side of the machine

4. Attach tooling (C) to the pressure tap for the pilot system pressure.

5. Attach a 34,450 kPa (5,000 psi) pressure sensor (B2) to fitting (C3) on tooling (C).

Test Procedure

1. Start the engine.

2. Place the engine speed control to the HIGH idle position.

3. Increase the hydraulic oil temperature to 50° ± 10°C (122° ± 18°F).

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

5. Move the joystick for the bucket to the full bucket OPEN position and HOLD in this position.

6. Check the pilot relief valve setting at the pressure tap. Refer to Table 2 for pilot relief pressure.

7. Return the joystick for the bucket to the NEUTRAL position.

8. If the pressure is not within the specification shown in Table 2, refer to "Test Procedure".

Adjustment Procedure

Illustration 4	g02650836
Pilot oil supply manifold located on the right side of the machine (A) Adjustment screw (L) Locknut

1. In order to adjust the pilot relief valve, loosen the locknut.

2. Turn the adjustment screw until the pressure reading at the pressure tap is within the specification.

   Note: Turn the adjustment screw clockwise in order to increase the pressure. Turn the adjustment screw counterclockwise in order to decrease the pressure.

   Note: Always make final pressure adjustments on pressure rise.

3. Tighten the locknut.

4. Test the pressure setting again. Refer to "Worksheet".

Worksheet