GB - 30
The pump and motor units require fluid
changes yearly or every 250 hours whichever
occurs first. The system filter should be
changed initially after the first 50 hours of
operation. The fluid and filter must be
changed and the system cleaned if the fluid
would become contaminated with dirt, water,
etc.
NOTE:
The integrated pump/motor units are
equipped with bypass valves. (See
Moving
the Unit with the Engine Off
on page 23.)
Changing Hydraulic Fluid
1. Park the machine on a level surface,
stop the engine, put the steering control
levers in the park position and remove
the key.
2. Clean the area around the reservoir filler
cap and remove the filler cap from the
reservoir.
3. To drain the hydraulic fluid, place a
suitable container under the hydraulic
filter and remove it.
4. Place a thin coat of hydraulic oil on the
gasket on the oil filter. Before
reinstalling, make sure mount area is
clean of debris.
5. Install the hydraulic oil filter onto the filter
adapter.
6. Refill the hydraulic reservoir to the
recommended level. Reinstall the oil
reservoir filler cap.
7. Clean up any fluid which may have
spilled.
Bleeding/Purging the Hydraulic
System
IMPORTANT:
Air in the hydraulic system is
the primary cause of hydraulic pump failures.
Following hydraulic system service or repair,
the hydraulic system MUST be correctly
purged of trapped air before placing the
mower back in operation.
1. To bleed the system make sure the oil
tank is full, the oil must barely cover the
fill baffle inside of the tank.
2. Raise the rear unit tires off the floor and
place it on suitable jack stands.
3. Open both pump bypass valves, one on
each pump, two full turns maximum.
4. Sitting in the operator’s seat, start the
engine and run it at idle.
5. Slowly cycle the steering control levers
full forward and full reverse for 10
seconds in each direction, 5 or 6 times.
NOTE:
The rear tires should rotate, but they’ll
not be under load.
6. Shut off the engine, check and add
hydraulic oil as necessary.
7. Close the bypass valves on both pumps.
Do not over tighten.
8. Sitting in the operator’s seat, start the
engine and run it at idle.
9. Slowly cycle the steering control levers
full forward and full reverse, 5 or 6 times.
NOTE:
It may be necessary to repeat purging
procedures until all air is vented out of the
hydraulic system. When the Pump moves
forward and reverse at normal speed and the
reservoir oil remains at a constant level,
purging is complete.
IMPORTANT:
The rear tires are now rotating
under power. Do not touch or contact them. If
they do not rotate after 2-3 cycles, stop
immediately. There may still be air in the
system. Let the pumps cool and try purging
again from
Step 1.
10. Shut off the engine, lower the unit back
to the floor and check and add hydraulic
oil as necessary.
Checking The Hydraulic Hoses
Inspect the hydraulic hoses every 250 hours
to ensure they are in good working order.
Check both the hoses and hose clamps to
ensure there is no wear or damage. If either
is found worn or damaged, repair or replace
them at once.
CAUTION:
Be sure the engine
has been stopped, the steering
control levers are in the park
position, and the key has been
removed before changing or
checking the hydraulic oil in the
mower.
Allow the hydraulic fluid to cool.
The oil may be hot and could
cause serious burns.
