HYDRAULICS
8N-46
NOTE:
Open tow valve after test is completed
(Figure 8N-1).
Figure 8N-1. Tow Valve
Conclusion
• If the traction wheels break traction, the traction
pump is not at fault.
• If the traction wheels do not break traction and
engine does not labor, a fault may exist in the
hydrostatic drive circuit, including the traction pump
or traction motors.
LIFT SYSTEM TEST
The purpose of this test is to determine if the lift cylin-
ders are bypassing fluid internally (Figure 8N-2).
1. Operate the mower until the hydraulic oil reaches
operating temperature, 110 – 130
°
F (43 – 54
°
C).
2. Lift the reels and shut down the engine.
3. Measure the distance between the bottom of a
reel and the ground.
4. Allow the mower to stand for 15 minutes.
Conclusion
• If the reels do not drop, the lift system has no
internal leakage.
• If any of the reels show signs of dropping, proceed
with the test.
NOTE:
Use a floor jack and board to support the reel,
being carefully not to damage the reel.
5. Lift and support the reel. Shut down the engine.
6. Disconnect the hydraulic hose from the extend
side of the lift cylinder. Immediately plug the
hydraulic hose.
7. Place a container underneath the cylinder (mini-
mum 1-gallon (3.8-liter)) capacity.
8. Slowly lower the floor jack and observe the cylin-
der extend side port.
Conclusion
• If the reel does not drop and hydraulic oil does not
flow from the cylinder, the cylinder is not bypassing
and the problem may be in the lift valve.
• If oil flows from the cylinder port and the reel drops,
the cylinder is bypassing oil and must be replaced or
repaired.
Figure 8N-2. Lift Cylinder Test
Retract Side
Floor Jack
Separate Hose
Cylinder
Extend Side
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