1241
Model Code Page
90. Hydraulic system
1. 11. 1998
6000--8750 911 1
1. 1. 1995
Repair instructions
1. Low pressure circuit
(Op. no. 911)
A. Measuring pressure
1. Start the engine and run it at 1500 revs/min.
2. Warm up the transmission/hydraulic oil to 40---65˚C.
Note! The oil warms up faster if the steering wheel is held
against the stop.
3. Disengage as many servo functions as possible (clutches
unpressurised in order to eliminate a pressure drop caused
by leakages in clutch piston seal s).
Note! When the 4WD is engaged, the clutch is unpressurised.
On 2---step speedshift should theTORTOISE range be enga-
ged (Trac---Trol) or HARE range engaged (Overdrive). On
HiTech models the shuttle must be in the neutral position. Two
DPS clutches are always pressurised,when the engine is run-
ning.
Pressure---test point
Pressure---limiting valve
4a. Earlier valve block (---660070): Connect a pressure gauge
to the test point on the servo valve block (on the LH side of the
gearbox). Read the pressure. It should be between 2,1---2,3
MPa. Pressure measuring equipment, see page 910/5.
Pressure---limiting valve
Pressure---test point
4b. Later valve block (660071---): Connect a pressure gauge
to the test point on the servo valve block and read the pres-
sure value. It should be 1, 8 ---1,9 MPa.
4c. On tractors which have been equipped with HiTech Shut-
tle, the low pressure circuit test point is placed on the outer
face of the valve block, see page 440/24. The pressure value
is 1,8---1,9 MPa.
Note! These pressures are maintained by the low pressure
limiting valve and seals at various soleno id valves (and clutch
piston seals in pressurised clutches).
Pressure---limiting valves (1,8 MPa)
---660070
660071---
5. If the pressure gauge reading deviates much from the cor-
rect value, the fault can lie in the pressure---limiting valve orthe
low---pressure pump is worn out. Also excessive leakage can
cause pressure loss.
6. Then activate each service in turn. The pressure should
momentarily drop but quickly re---stabilise. A constant pres-
sure drop of about 0,1---0,2 MPa indicates excessive leakage
and therefore pressure loss in that service.
Note! Pressure measuring equipment, see page 910/5. It is
available a pressure---test kit which order no is 31965000. It
includes all equipment needed for pressure measurement on
Valmet tractors. The parts can also be ordered separately.
To Next Page
Loading...
