SkyTrak 6036 Service Manual - Manual (Page 121)

Section 9. Hydraulic System
Model 6036 S/N 9B0499 and Before 9-8
Fig. 9.4 Grille Tilt and Slave Circuit
6. Repeat steps 4 and 5 to recheck performance.
7. If the boom extend/retract circuit test does not
meet performance requirements, locate the
cause of the problem and correct before
putting the vehicle into service.
9.1.3 Grille Tilt and Slave Circuit
a. Description
Hydraulic pressure is applied in the grille tilt and
slave circuit by the 30 gpm section (rear half) of
the tandem pump, which draws its fluid through a
suction screen in the reservoir, Fig. 9.4. Pressure
is directed to either side of the grille tilt and slave
cylinder pistons by the shifting of a spool in a
directional control valve found in the main control
valve assembly. The spool is shifted by the grille
and frame tilt control lever and its associated
control cable. Control lever positions for tilting the
grille are as follows:
Center Position
When the grille and frame tilt control lever is
placed in the center or neutral position, the
directional control valve spool is positioned so that
pump supply pressure is directed through ports F
to C, Fig. 9.4, to the return filter and reservoir. If
the return filter becomes clogged, hydraulic oil will
bypass the filter when the pressure reaches 10 to
15 psi
(0,7 to 1,03 bar).
Up Position
When the grille and frame tilt control lever is
placed in the “up” position, the directional control
valve spool is positioned so that pump supply
pressure is directed through ports E to A, Fig. 9.4,
to the base (extend) end of the grille tilt and slave
cylinders. The extension of the slave cylinder is
fixed by the position of the boom so that only the
grille tilt cylinder is extended to tilt the grille up. If
supply pressure reaches 2650 psi (182,6 bar), the
TO BOOM HOIST
CYLINDER
TO BOOM EXTEND
CYLINDER
TO FRAME TILT
CYLINDER
GRILLE TILT CYLINDER
SLAVE
CYLINDER
GRILLE TILT PORT
RELIEF VALVES
TANDEM
PUMP
RESERVOIR
STRAINER RETURN
FILTER
DIRECTIONAL CONTROL VALVE
POSITIONS
MAIN CONTROL
VALVE
A B C A B C A B C
D E F D E F D E F
CENTER
15
GPM
30
GPM
0-4000 psi
PRESSURE
GAUGE
DOWN DOWN UP
UP
MA0452
COUNTER-
BALANCE
VALVE