Internal Expansion Tank (Iet) - Hydro-Gear ZT-2800 Service And Repair Manual

INTERNAL EXPANSION TANK (IET)

Refer to Figure 22
Transaxles with a "T" in the 13th character position of the model code are equipped with
an internal expansion tank (195).
The internal expansion tank (IET) is similar to a siphoning expansion tank. Instead of
a siphon tube, there is a riser tube. As the transaxle heats up, the oil in the main case
expands and pushes down the riser tube. At the bottom of the riser tube is a two-way
valve. Oil coming from the riser tube builds about 1-2 psi in the main case to open the
umbrella style valve and allow oil to flow into the expansion tank. When the transaxle
cools, the oil condenses which creates a very slight vacuum. This pulls oil from the ex-
pansion tank through the two-way valve duckbill, directly into the main case. Similar to
the siphon tube design hot oil goes out of the main case at the top of the tube and cool
oil returns from the bottom of the expansion tank.
Removal of the internal expansion tank (195) and the breather vent (194) is not neces-
sary while performing service and repair to the unit.
Breather Vent (194)
Internal Expansion Tank (195)
28
Figure 22, Internal Expansion Tank
Top Port Plug (5)
ZT-2800 /ZT-3100
®
/ZT-3200
® TM