Service Manual

7-8
Digital Edition - TITAN® HD Service Manual
January 2018
Table of Contents
HYDROSTATIC DRIVE SYSTEM
Purging Procedure
Due to the effects air has on efciency in hydrostatic drive applications, it is critical that it be purged from the
system. This purge procedure should be implemented any time a hydrostatic system has been opened to facilitate
maintenance, any additional oil has been added to the system, or a replacement transaxle has been installed. Air
creates inefciency because its compression and expansion rate is higher than that of the oil in hydrostatic drive
systems.
The resulting symptoms in the hydrostatic system may be:
-noisy operation.
-lack of power or drive after a short period of operation.
-high operating temperature and excessive expansion of oil, in the latter case, oil level may be high in the
expansion tank or overow.
The following procedure should be performed with the wheels off the ground and then repeated under operating
conditions.
1. With the bypass valve open (push position) and the engine running, slowly move the directional controls
(forward/reverse levers) in both forward and reverse directions 5-6 times, as air is purged from the transaxles,
the oil level will drop.
2. With the bypass valves in the closed position (run position) and the engine running, slowly move the directional
control levers in both forward and reverse directions 5-6 times.
3. It may be necessary to repeat steps 1 and 2 until all air is completely purged from the transaxles. When the
transaxles move forward at normal speed, purging is complete.