Bolens 140-990A - Manual (Page 22)

HYDROSTATIC TRANSMISSION TROUBLE SHOOTING
1. Recheck relief valve position, control linkage, input drive. No output torque (power) in either
direction, cold start.
Loss of output torque, continous 1.
load.
2 .
3.
No output torque in one direction.
Riding mower cannot be pushed
with engine off.
No neutral.
Noisy Operation.
Output shaft rotates in the op­
posite direction.
2. Oil level in reservoir low.
3. Broken control shaft dowel pin. Transmission must be repaired or re­
placed.
Operating at conditions approaching hydraulic stall. The transmission
fluid has exceeded 180°F.
Internal leakage due to wear. Transmission should be repaired or re­
placed.
Water in transmission fluid. Purge system of all fluid and replace with
new transmission fluid. Replacement of the transmission is generally
not necessary.
One of the directional valves is stuck. Transmission should be repaired
or replaced.
Low oil level.
1
2
1. Relief valve control not set.
2. Relief valve travel not adjusted.
3. Motor piston or rotor seized. Transmission must be repaired or replaced.
1. Recheck linkage. Loose linkage creates an adjustment problem.
Note: The hydraulic neutral band is very narrow. Deflection in the
linkage may make it difficult to obtain neutral from both direc­
tions. It is recommended that neutral should be positive from for­
ward drive.
Oil leakage at the control shaft 1.
seal.
2 .
Spillage when fluid has been added to the reservoir.
Spillage at the vent in the reservoir at operating temperatures due to cold
level being too high or water in the fluid. Reduce fluid level or replace
fluid in the event there is water in it (milky color).
Loose oil reservoir or cover.
Loose vent bolt.
Damaged control shaft seal. Transmission should be repaired.
1. Operating at part throttle. Hydrostatic transmission is designed to
operate with the engine running at full throttle.
2. Water in transmission fluid. Replace transmission fluid.
3. Air in transmission fluid. Bleed airfrom vent.
1. The transmission body is 180° out of position. Transmission has to be
removed and reassembled correctly.
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