Bleeding The Hydraulic System - Toro GrandStand 74534 Service Manual

Bleeding the Hydraulic System

Due to the effects air has on efficiency in hydrostatic
drive applications, it is critical that air is purged from the
system.
These purge procedures should be implemented any-
time a hydrostatic system has been opened for main-
tenance or any additional oil has been added to the
system.
Air creates inefficiency because it has compression and
expansion rates that are higher than that of oil.
Air trapped in the oil may cause the following symptoms:
• Noisy operation
• Lack of power or drive after short-term operation
• High operation temperature and excessive
expansion of oil.
Before starting, make sure the reservoir is at the proper
oil level.
The following procedures should be performed with the
vehicle drive wheels off the ground, then repeated under
normal operating conditions.
WARNING
!
POTENTIAL FOR SERIOUS INJURY
Certain procedures require the vehicle engine
to be operated and the vehicle to be raised off
of the ground. To prevent possible injury to the
servicing technician and/or bystanders, ensure
the vehicle is properly secured.
36" & 40" Toro GrandStand Service Manual
HYDRAULIC DRIVE SYSTEM
1. Disengage the PTO.
2. Stop the engine and wait for all moving parts to stop
before leaving the operating position.
3. Support the rear of the machine on jack stands high
enough to raise the drive wheels off the ground.
4. With the bypass valve open and the engine running,
slowly move the directional control in both forward
and reverse directions (5 to 6 times). As air is purged
from the unit, the oil level will drop.
5. With the bypass valve closed and the engine
running, slowly move the directional control in both
forward and reverse directions (5 to 6 times). Check
the oil level, and add oil as required after stopping
engine.
6. It may be necessary to repeat Steps 4 and 5 until all
the air is completely purged from the system. When
normal forward and reverse speed is obtained,
purging is complete.
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