314D Excavator Hydraulic System Caterpillar

Illustration 1	g01872217
Blade control valve (load sensing) (1) Pressure tap (delivery pressure for the blade pump) (2) Blade main relief valve (3) Line relief valve (rod end of blade cylinder) (4) Line relief valve (head end of blade cylinder)

Illustration 2	g01872493
Blade control valve (standard) (1) Pressure tap (blade pump) (2) Blade main relief valve (5) Overload relief valve (blade cylinder)

Illustration 3	g01872498
Relief valve (typical example) (6) Locknut (7) Adjustment screw

Blade Main Relief Valve

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".

4. Connect a 60000 kPa (8700 psi) pressure gauge to pressure tap (1) .

5. Start the engine.

6. Place the machine controls at the following settings: engine speed dial "10" and AEC switch OFF. Refer to Testing and Adjusting, "Engine Performance - Test (Engine Speed)" for engine rpm settings.

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

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

9. Slowly move the blade control lever to the full RAISE position and check the pressure gauge reading at pressure tap (1) . Refer to Table 1 for the specification.

10. Return the blade control lever to the NEUTRAL position.

11. If the setting of the blade main relief valve is not within the specification, adjust the relief valve. Refer to Table 1.

12. In order to adjust blade main relief valve (2) , loosen locknut (6) and turn adjustment screw (7) until the pressure gauge reading at pressure tap (1) is the correct relief pressure.

    Note: Turning adjustment screw (7) clockwise increases the pressure. Turning adjustment screw (7) counterclockwise decreases the pressure.

    Note: Always make final pressure adjustment on pressure rise.

13. Tighten locknut (6) .

Blade Line Relief Valve

Note: A temporary setting of the blade main relief valve is required before the blade line relief valve is adjusted.

Note: Refer to Testing and Adjusting, "Specifications" for the pressure setting of the blade relief valves.

1. Connect a 60000 kPa (8700 psi) pressure gauge to pressure tap (1) .

2. Perform the following steps in order to make a temporary adjustment to the blade main relief valve.

   1. Move the blade control lever until the blade is at the full RAISE position (full retraction of the blade cylinder). Hold the blade control lever in this position.

   2. Check the pressure setting of the blade main relief valve at pressure tap (1) .

   3. Return the blade control lever to the NEUTRAL position.

   4. Loosen locknut (6) on blade main relief valve (2) . Turn adjustment screw (7) until the pressure gauge reading at pressure tap (1) is 27500 kPa (4000 psi).

      Note: Turning adjustment screw (7) clockwise increases the pressure. Turning adjustment screw (7) counterclockwise decreases the pressure.

      Note: Always make final pressure adjustment on pressure rise.

   5. Tighten locknut (6) .

3. To adjust the pressure setting of the blade line relief valve, move the blade control lever to the full LOWER position (full extension of the blade cylinder). Hold the blade control lever in this position.

4. Check the line relief valve pressure setting of the blade cylinder at pressure tap (1) .

5. Return the blade control lever to the NEUTRAL position.

6. Loosen locknut (6) on the blade line relief valve. Turn adjustment screw (7) until the pressure gauge reading at pressure tap (1) is within the specification. Refer to Table 1.

   Note: Turning adjustment screw (7) clockwise increases the pressure. Turning adjustment screw (7) counterclockwise decreases the pressure.

   Note: Always make final pressure adjustment on pressure rise.

7. Tighten locknut (6) .

8. Return the pressure setting of the blade main relief valve to specification after adjusting the blade line relief valve. Refer to Table 1 for the pressure setting of the blade main relief valve.