Bleeding The Hydraulic System - Toro 30284 Service Manual

HYDROSTATIC DRIVE SYSTEM

Bleeding the Hydraulic System

Due to the effects air has on effi ciency 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 to facilitate
maintenance or any additional oil has been added to the
system.
Air creates ineffi ciency because it has compression and
expansion rates that are higher than that of oil.
Entrained air 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. If it is not, fi ll to the vehicle manufacturer's
specifi cations.
The following procedures should be performed with the
vehicle drive wheels off the ground, then repeated under
normal operating conditions.
6
!
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, insure
the vehicle is properly secured.
6-32
WARNING
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
the BDP's move forward and reverse at normal
speed purging is complete.
Cleanliness is a key factor in the successful repair of
BDP's. Thoroughly clean all exposed surfaces prior to
any type of maintenance. Cleaning of all parts by using
a solvent wash and air drying is usually adequate. As
with any precision equipment, all parts must be kept free
of foreign material and chemicals. Protect all exposed
sealing areas and open cavities from damage and
foreign material.
Upon removal, all seals, O-rings, and gaskets should
be replaced. During installation, lightly lubricate all
seals, O-rings, gaskets with clean petroleum jelly prior
to assembly. Also protect the inner diameter of seals by
covering the shaft machined features with plastic wrap or
equivalent.
Floating Deck Mid-Size Service Manual