Oil Level Control Valve
The oil level control valve is located on the bottom of the case next to the fluid filter, and is designed to control the fluid level in the side cover. At low temperatures, the thermostatic element exerts little pressure on the thermostatic element plate allowing fluid to drain into the sump (left balloon). As the temperature of the fluid increases, the thermostatic element begins to apply pressure to the thermostatic element plate, thereby trapping fluid in the side cover (right balloon). This level of transaxle fluid is required in order to maintain the operation of the hydraulic system in the transaxle.
It should be noted that when checking the fluid level, it will be higher when the transaxle is cold. Conversely, the fluid level will drop when checked at operating temperatures. Thus, the fluid level of the transaxle must be checked when the fluid is at operating temperature.