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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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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. |
| "Relief Valve (Main) - Test and Adjust" | |||
|---|---|---|---|
| Date | Machine Serial Number | ||
| Machine Settings | Engine Speed | ||
| Speed Dial "10"
AEC switch OFF |
|||
| Item | Specification | Actual | |
| Main Relief | Implement | |
|
The main relief valve is located on the left side of the main control valve towards the top. The main relief valve limits the maximum operating pressure of the travel hydraulic circuit and the implement hydraulic circuits when the machine is at a load condition.
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| Illustration 1 | g02197334 |
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(1) Pressure tap
(2) Main relief valve | |
| |
| Illustration 2 | g01623868 |
|
Tooling group "B" 198-4240 Digital Pressure Indicator Gp | |
| Tool | Item | Part Number | Description | Qty |
|---|---|---|---|---|
| B | 198-4240 | Digital Pressure Indicator Gp | ||
| B1 | 198-4234 | Indicator | 1 | |
| B2 | 198-4238 | Pressure Sensor
|
1 | |
| B3 | 198-4236 | Extension Cable | 1 | |
- Position the machine on level ground and stop the engine.
- Release the pressure in the hydraulic system. Refer to Testing and Adjusting, "Hydraulic System Pressure - Release".
- Open the door for the main control valve compartment in order to access the pressure tap and the main relief valve.
- Attach a
34,450 kPa (5,000 psi) pressure sensor to the pressure tap (1).
- Start the engine.
- Place the engine speed controls in the HIGH IDLE position. Refer to Testing and Adjusting, "Engine Performance - Test (Engine Speed)".
Note: The engine will not reach maximum no-load speed until the hydraulic tank pressure has reached the operating level.
- Increase the hydraulic oil temperature to
55° ± 5°C (131° ± 9°F) . - To check the main relief valve pressure setting at pressure tap (1), move the joystick for the bucket until the bucket is at the full BUCKET CLOSE position (full extension of bucket cylinder). Hold the joystick for the bucket in this position.
- Check the pressure reading at pressure tap (1).
- The pressure reading should be
24500 - 26000 kPa (3550 - 3800 psi) . - Return the control lever to the NEUTRAL position.
- To adjust the main relief valve pressure, loosen locknut (3) and turn adjustment screw (4) until the pressure reading at pressure tap (1) is
24500 - 26000 kPa (3553 - 3771 psi) .Note: Turning adjustment screw (4) clockwise increases the pressure. Turning adjustment screw (4) counterclockwise decreases the pressure.
Note: Always make final pressure adjustments on pressure rise.
- Tighten locknut (3) to a torque of
50 ± 10 N·m (37 ± 7 lb ft) .
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| Illustration 3 | g01357347 |
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Main relief valve (typical example) (3) Locknut (4) Adjustment screw | |