Thomas T175 - Hydraulic System

8
8-9
Hydraulic
action jerky
Boom raises
slowly at full
engine rpm
Lift or tilt
cylinders will
not support a
load
Hydraulic oil
overheating
Reservoir low on
oil
Air in hydraulic
system
Anti-cavitation
check valve not
functioning
Reservoir low on
oil
Foot pedal linkage
binding
Auxiliary foot
pedal engaged
Engine RPM too
slow
Anti-cavitation
check valve spring
broken
Pressure relief
valve in control
valve faulty
Internal leakage in
pump due to wear
Oil bypassing one
or both lift cylin-
der piston seals
External leak
between or at con-
trol valve and
cylinders
Control valve
spool not center-
ing
Oil leaking by one
or both cylinder
piston seals
Reservoir low on
fluid
Oil cooler plugged
or dirty (also
check engine radi-
ator)
Replenish with 10W30
API or 20W50 SF oil.
Check for leak
between reservoir
and pump. Bleed system
by extending and retract-
ing lift cylinders several
times.
Inspect and repair or
replace
Replenish with 10W30 or
20W50 API SJ oil
Inspect and adjust
Disengage
Check RPM and reset
Replace
Check pressure if neces-
sary - adjust
Check pump flow and
repair or replace as neces-
sary
Install new piston seal kits
Check for leaks and cor-
rect
Check for sticking foot
pedal linkage
Check for broken or stuck
return spring on valve
spool
Install new piston seal kits
Replenish with 10W30 or
20W50 API SJ oil
Clean cooling fins
TROUBLESHOOTING 8.2
Symptom Cause Remedy
8.2D Hydraulic System
Symptom Cause Remedy
Loss of
hydraulic
power (no
flow from
gear pump)
Loss of
hydraulic
power (flow
from gear
pump)
Reservoir low on
fluid. Hose or fitting
leak.
Universal Joint
between engine and
pump failure
Spline coupling fail-
ure between front
and rear hydrostatic
pump
Hydraulic gear pump
not functioning
Reservoir low on
fluid
Foot pedal linkage
disconnected or bind-
ing
Auxiliary foot
pedal engaged
Relief valve failure
in control valve
Replenish with 10W30
or 20W50 API SJ oil.
Check for leaks.
Inspect and replace
damaged parts. Check
for misalignment
between engine and
pumps.
Inspect coupling for
sheared splines. Also
check pump shaft
bearings.
Inspect and repair.
Replenish with 10W30
or 20W50 API SJ oil
Inspect and adjust.
Disengage
Check pressure and
adjust.
8.2D Hydraulic System
Hydraulic oil
overheating
Foot pedals
do not oper-
ate smoothly
Auxiliary foot pedal
engaged
Engine RPM too
slow
Incorrect temperature
sensor
Foot pedal linkage
out of adjustment
Foot pedal linkages
need lubrication
Disengage
Check RPM and
adjust
Replace
Adjust foot pedal link-
ages
Lubricate with a sili-
cone based lubricant