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Shaft Seal Leak Causes
HIGH BACK PRESSURE IN THE RETURN LINE:
This is the most common cause of shortened motor seal life. the hydraulic motor seal is rated for 250 pssi of back pressure. However, a
continuous return pressure of 100 psi or less is recommended for efficient operation and optimum seal life. The high return pressre is
caused by restrictions in hoses, fittings, and tractor plumbing.
LOOK FOR:
Seal lips pressed tight against the outer seal housing and shaft. There may also be grooves in the shaft
where the seal ips touch.
PREVENTION:
The best way to minimize return pressure is to return oil directly back to the tractor reservoir. Most tractor
manufacturees now offer a Low Pressure REturn Port option for this purpose. Contact your dealer for
the specific options available for your tractor model. Preper hydraulic hose sizing in also important to
minimize restriction. A open hose coupling may also be used to reduce restrictions in the return line. Ace
recommends 1/2" hose for 200 Series motors and 3/4" hose for 300 series motors. The hoses should be
sized larger if individual lengths exceed 15 feet.
PRESSURE SPIKE:
System pressure spikes may also damage the shaft seal and cause leakage. Spikes in the 3000-5000 psi range may result from
imporperly synchronized hydraulic valves or quick couplers coming unplugged during operation.
LOOK FOR:
The seal lips are pressed tight against the outer seal housing and form a right angle between the seal
housing and the shaft. In severe cases, the seal lip material may be extruded between the front seal
casing and the shaft.
PREVENTION:
Using a Low Pressure Return Port prevents spikes by keeping the return line open back to the reservoir at
all times. If not using a low pressure return, the pump should always be turned off by moving the lever to
the Float position. When moved to Float, the oil supply valve is shut but the return valve stays open.
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