Purging Procedures - Hydro-Gear ZT-2800 Service And Repair Manual

pUrging prOCedUres

Due to the effects air has on efficiency in hy-
drostatic drive applications, it is critical that it is
purged from the system.
Air creates inefficiency because its compres-
sion and expansion rate is higher than that of
the oil approved for use in hydrostatic drive
systems.
These purge procedures should be imple-
mented any time a hydrostatic system has been
opened to facilitate maintenance or the oil has
been changed.
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.
Before starting, make sure the transaxle is at
the proper oil level. If it is not, fill to the specifi-
cations outlined in this manual.
12
The following procedures are best performed
with the vehicle drive wheels off the ground.
Then repeated under normal operating condi-
tions. If this is not possible, then the procedure
should be performed in an open area free of
any objects or bystanders.
1. Disengage the brake if activated.
2. With the bypass valve open and the engine
running, slowly move the directional control
in both forward and reverse directions (5 or
6 times).
3. 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 the engine.
4. It may be necessary to repeat Steps 2 and
3 until all the air is completely purged from
the system. When the transaxle operates
at normal noise levels and moves smoothly
forward and reverse at normal speeds, then
the transaxle is considered purged.
ZT-2800 /ZT-3100™/ZT-3400™
®