Valtra 6000 Workshop Manual page 1303

91. Hydraulic system
C. Fault tracing without removing pump
If the hydraulic system functions when the oil is cold, but in the
operating temperature different functions are slow or power-
less, this indicates that the oil pump is worn ---out.
The high pressure pump can be tested by connecting a pres-
sure gauge to the circuit and by pulling one auxiliary hydraulic
valve lever to the pressure position. Now if the pressure gauge
reading follows clearly the engine revs alteration, this indi-
cates that the pump is worn.
The faulty pump can be noisy which indicates a damage in the
pump. Note that a blocked suction strainer causes a shrieking
sound to the pump.
A worn pump "whips" oil and due to the fluid friction the whole
hydraulic system overheats. This can be verified by feeling the
temperatures of the pipes and the oil reservoir. In this case, for
instance, the pump pressure pipe can be essentially warmer
that other pipes and the oil reservoir.
D. Internal inspection of pump
Note! Never dismantle the pump if the warranty is valid, but
in this case change a new spare pump.
1. Detach the damaged pump from the tractor. Make sure
that the pump and a fitting table are clean before dismantling
the pump.
3. Mark all removed parts in relation to each other for easier
assembling.
4. Fit always new seals. A seal kit no. 32664100 is available for
the pump.
Note! When the hydraulic system is in a perfect condition, the
pump housing surfaces are smooth and shiny as well as the
bearing surfaces. Text below presents how faults in the
hydraulic system affect the oil pump.
---
1. Impurities in oil Impurities cause clear dragging
grooves on the pump housing and bearing surfaces in the
direction of rotation. The most evident damage caused by
impurities are deep grooves on the gearwheel side surfaces.
Impurities wear the pump fast resulting lowered output value.
---
2. Cavitation damages Mineral oils contain 10 percent of
air. In the pump suction side if suction is too high, air bubbles
are formed, which fasten onto the pump housing. When pres-
sure in the pressure side rises rapidly, the bubbles "explode"
causing deep pits on the pump housing. In certain cases the
cavitation generates sound, which can be heard from the
pump.
Possible reasons:
1. Suction pipe or suction strainer blocked.
2. Wrong oil viscosity.
3. Air enters into system.
1. 1. 1995
15. 5. 1995
3. Air in oil --- If air enters into the system via the suction side
or via the pump drive shaft seal, this causes the same dam-
ages as cavitation. If there is too much air in oil, the oil in the
reservoir foams.
4. Pump drive shaft loading --- If the pump drive shaft has
a strong radial loading caused by the pump drive mechanism,
this causes damages to the shaft seal and air and oil leaks by
the seal and after a prolonged use, the drive shaft bearings are
worn unevenly. For the same reason, the pump gears cut the
pump housing on one side resulting internal leakages in the
pump.
Observe the following when assembling the pump
Assemble the low pressure pump and tighten the end cover
bolts to a correct torque. Assemble the high pressure pump
and tighten the end cover bolts only to finger tight. Blow com-
pressed air (~ 5 bar) through the pressure side hole (suction
side hole open) at which time the shafts and gear wheels are
centered and at the same time tighten the end cover bolts to
a correct torque of 61 ---68 Nm.
Note! Without this centering the pump will probably damage
after a very short operating time.
E. Maintenance
1. Check the hydraulic oil weekly/at every 50 running hours.
Oil quality: 10W/30, 5W/30 or 5W/20, API GL ---4 (STOU)
according to the outdoor temperature.
2. The pressure filter is changed the first time at 100 hours war-
ranty service. The second change is done at 250 running
hours and the third change at 500 running hours. After that
the filter is changed at every 500 running hours.
3. Hydraulic oil should be changed at intervals of 1000 run-
ning hours or yearly which one is reached first. The suction
strained should be cleaned always when the oil is changed.
The suction strainer should be changed more often when
necessary.
Note! If You use continually the auxiliary hydraulics, the
hydraulic oil and the pressure filter should be changed more
often.
4. The high pressure and the low pressure can be measured
according to instructions. Also different clutch pressures can
be checked. The pressure limiting valve and the shock valve
can be opened and cleaned. These valves can also be
adjusted by changing shims.
Important! If the hydraulic power lift or the Delta Powershift
have malfunctions, the pressure filter insert should be
changed immediately.
1246
Model Code
6000-- 8750 911
Page
6