Service Manual

310-3000 IHT 11
PURGING PROCEDURES
Due to the effects air has on efficiency in hydro-
static drive applications, it is critical that it be
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 inefficiency because its compression
and expansion rate is higher than that of the oil
normally approved for use in hydrostatic drive
systems.
The resulting symptoms in hydrostatic systems
may be:
1. Noisy operation
2. Lack of power or drive after short term op-
eration
3. High operation temperature and excessive
expansion of "oil", in the latter case, oil may
overflow.
Before starting, make sure the transaxle/ trans-
mission is at the proper oil level. If it is not, fill to
the manufacturers suggestions outlined in the
vehicle owners manual.
The following procedures should be performed
with the vehicle drive wheels off the ground, then
repeated under normal operating conditions.
1. 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 and bubbles may appear in the
oil. After stopping the engine, add oil, as nec-
essary. Fill to the level outlined in Figure 3,
Page 7.
2. 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 re-
quired after stopping engine.
3. It may be necessary to repeat Steps 1 and 2
until all the air is completely purged from the
system. When the transaxle moves forward
and reverse, purging is complete.
CAUTION
DO NOT OVERFILL.
If you overfill the transaxle while the unit
is "cold", it may overflow as it reaches
normal operating temperatures. The oil
level should not be above the level
shown in figure 3, Page 7. This will allow
the space needed for the oil to expand
as it warms up.