HYDRAULIC SYSTEM 5540F/YB5515 SERVICE MANUAL
4-26 Published 10-21-2010, Control# 198-04
Crowd Cylinders Leakage Test
If the cylinders does not hold the load, the problem is
normally internal leakage in the cylinders. This problem can
also be caused by leakage in the control valve or the holding
valve. To check for leakage in the cylinders:
1. Raise the boom a little above the horizontal position.
2. Fully extend the boom.
3. Stop the engine. Move the control lever several times in
each direction to release any hydraulic pressure in the
circuit.
4. Disconnect the hydraulic hose from bulkhead elbow
Figure 4-27 which connects to the rod port of the crowd
cylinder. A little oil will drain from the elbow.
5. Start the engine. Actuate the control lever in the direction
to extend the boom. Check the amount of leakage from
the bulkhead elbow. If the leakage is more than a few
drops per minute, replacement of the piston seals is
necessary.
Hydraulic Swivel
See Hydraulic Swivel information in this section.
MAIN WINCH CIRCUIT
General
The main winch circuit includes the winch motor, a brake, a
brake holding valve, ports 1 and 2 of the hydraulic swivel, an
anti-double block solenoid valve, the spool section of the
control valve and the hydraulic lines.
Oil Flow
When the valve spool in the neutral position, both A and B
ports are closed. Oil is held in the winch circuit, inhibiting
movement of the winch motor.
Winch Up
Pulling the handle spool IN routes oil from the front pump to
port B of the spool in the control valve Figure 4-28. From
here the oil is routed through swivel port 1 to the brake
holding valve. In this direction, the oil flows freely through the
brake holding valve to the winch motor.
During this operation the brake is not released, since the
load is driven through a one-way cam clutch in the winch,
bypassing the brake. When the winch comes to a stop, the
cam clutch locks up and is load is inhibited from moving by
the brake.
The anti-double block solenoid valve will shut off the oil
supply to the winch motor in the event the hook block comes
in contact with the boom head. In this case the operator must
lower the hook block before the boom can be raised or
extended.
The oil turns the motor and returns through swivel port 2 to
the control valve. From here, the oil is sent back through the
filter to the hydraulic tank.
Winch Down
Pushing the handle spool OUT sends oil from cylinder port A
of the spool in the control valve though swivel port 2 to the
winch motor Figure 4-29. The motor starts to turn, and the
increase in pressure on the up stream side of the motor
causes the brake holding valve to open and also the winch
brake to disengage. The oil then returns through swivel port
1 to the control valve and back to the tank.
Drain Line
A drain line is connected to the winch motor and returns
drain oil from the motor through swivel port 7 back to the
hydraulic tank.
Reference Only
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