GROVE 4-29
CD3340B/YB4411 HYDRAULIC SYSTEM
Published 04/07/2015 Control # 569-00
When the pressure is high enough to overcome the spring in
the counterbalance valve plus the pressure in the cylinder
base end, the counterbalance valve opens and the cylinder
retracts.
If the cylinder starts to retract too rapidly, for example,
because of heavy load on the cylinder, pilot pressure from
the rod end of the cylinder decreases and the load-holding
valve closes. The cylinder stops retracting temporarily until
enough oil is again available to the rod side of the cylinder. In
this way, cylinder cavitation is prevented and the load is held.
NOTE: The engine must be running to retract the
outriggers. The counterbalance valves inhibit
retracting the outrigger jacks simply from the
weight of the crane.
Vertical Outrigger Cylinder Leakage Test
If a vertical outrigger cylinder will not hold under load, the
problem is either the counterbalance valve or internal
cylinder leakage. To check for internal leakage in the
cylinder:
1. Start the engine and engage the parking brake.
2. Fully lower the outrigger.
3. Shut off the engine.
4. Remove the hydraulic line from the rod port of the
vertical outrigger cylinder.
5. Start the engine and actuate the control in the direction
to lower the outrigger. Check the amount of leakage
from the open port. If the leakage is more than a couple
of drops per minute, replacement of the piston seals is
recommended.
COMPONENT REPAIR
Hydraulic Pump Repair
Removal
1. Place a vacuum on the hydraulic tank to keep the
hydraulic fluid from draining when the hydraulic pump is
removed. If a vacuum can not be obtained drain the
hydraulic tank.
2. Remove the two socket head capscrews securing the
pump support bracket to the rear of the pump.
3. Remove the six capscrews securing the pump support
bracket to the engine. Remove the pump support
bracket.
4. Disconnect the suction line and pressure line from the
primary pump (Figure 4-16). Disconnect the load sense
and drain lines from the pump. Cap and plug all hoses
and ports.
5. The pump is heavy. Support the pump before removing
any attachment hardware. Remove the pump mounting
hardware. Remove the pump.
The hydraulic pump is not a field repairable component. The
pump must be sent back to the pump manufacturer for
repair. Contact your distributor for return information.
1. Attach the pump fittings to the pump before installing the
pump to engine. Check the O-rings on the inlet and
outlet hose fittings. If damaged replace the O-rings.
2. Align the spline of the pump shaft with the spline of the
pump coupler on the engine. Position the pump with the
compensator at the bottom of the pump. Install the
mounting hardware. Tighten the bolts to 88 Nm (65 lb-ft).
3. Attach the suction and pressure hoses to the pump.
4. Install the pump support bracket to the pump and
engine. Install the bracket to the engine using existing
hardware. Do not tighten the capscrews at this time.
5. Tighten the six pump bracket to engine mounting
capscrews to 93.8 Nm (69 lb-ft).
6. Connect the load sense line to the pump compensator.
Make sure the hose is routed under the pump support
bracket.
7. Connect the pump drain line to the pump. Make sure the
hose is routed above the pump support bracket.
8. Fill the hydraulic tank with clean filtered hydraulic oil.
NOTE: The variable displacement pump and all other
components require clean, filtered hydraulic oil for
proper operation. Contaminated hydraulic oil may
cause damage to the pump and other components.
Before adding any oil to the hydraulic tank, be sure
Reference Only
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