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Hydraulic System
from Daewoo Doosan 430 440 Plus 450 460 Series Hydraulic & Hydrostatic Systems Skid Steer Loader Service
WARNING
Hydraulic oil under pressure can remain in the system after the engine has been stopped. Personal injury can be caused if this pressure is not released from the system before any work is started. To be sure that the system is not pressurized, lower the boom to the ground with the engine off move the control pedals back and forth several times. This will release any pressure left in the system after shutting off the engine. The procedure must be done before any fitting, hose, or component is loosened. Perform adjustments on level ground away traffic. When making adjustments or taking measurements with the engine running, make sure that all personals clear of the machine.
Check & Adjusting Procedure of Relief Pressure of Control Valve
1. If attachment is installed on the truck, take it out from truck.
2. Check the engine speed. It should be within the following range.
Model rpm
430 Series 2,950 ± 50 440 Plus 2,780 ± 50 450 Series, 460 Series 2,800 ± 50
3. Warm the hydraulic oil to the temperature 100120°F (50 ± 5°C).
4. With the engine off, install 5000 psi (350 bar) rated pressure gage into the female coupler of the auxiliary hydraulic line(down side) on the boom.
5. Start the engine and at high idle, push the auxiliary. With keeping depressing the left side of thumb button on right driving control lever after pushing “On” switch of attachment on control panel, read the pressure gage.
6. The pressure gage should read the following range.
Model psi bar
430 Series 2,392 (+70) 165 (+5) 440 Plus 2,840 (+70) 195 (+5) 450 Series 2,840 (+70) 195 (+5) 460 Series
7. If the relief pressure does not fall into the above range, do the steps that follow.
a. With the engine off, locate the adjustment screw on the control valve.
b. Loosen the lock nut and turn the adjustment screw approximately 1/8 turn. The adjustment screw is very sensitive, do not rotate it over 1/4 turn at a time. To increase the relief pressure, tighten the adjustment screw clockwise. To decrease the relief pressure, loosen it.
c. Retighten the lock nut and, check out the relief pressure with above procedure. If the relief pressure still does not fall in the specific range, shut off the engine and adjust again. Repeat until the relief pressure falls into the specific range.
Adjustment Screw
Lock nut
A1 A3 A2
IN
B1 B2 B3
IGAT0825I
