2000 SRM 1233
Manifold, Section 1 of Hydraulic Plate
BRAKE MANIFOLD, SECTION 4 OF
HYDRAULIC PLATE
The brake manifold regulates and directs the flow of
oil for the brake cooling circuit, service brake, and
parking brake.
Cooling Circuit
Cooling oil for the oil-cooled brakes comes from the
cover end 48 cm
3
(2.94 in.
3
) tri-section pump. This
oil flows through the thermostatic bypass valve to the
service brakes at each drive wheel. If the oil is above
70 C (158
F)
, the valve will direct the oil through the
air-to-oil heat exchanger before it goes to the brakes.
A check valve keeps the pressure in the brake as-
semblies to less than 140 kPa (20 psi). Oil from the
brakes returns through a filter (20 micron), with a
35 kPa (5 psi) bypass, to the hydraulic tank.
Service Brake
Oil for activating the service brake comes from the
cab manifold. The service brake pedal (treadle valve)
controls the pressure of the oil to the service brake
piston at each drive wheel.
The pressure of the hydraulic oil supplied to the
brake manifold can be checked at check port MSB4,
integrated in the cab manifold.
The hydraulic line also functions as a return line
when the brake treadle is not operated. Oil flows
back through the brake treadle and return manifold
to the hydraulic tank.
Parking Brake
Oil for releasing the parking brake comes from the
main manifold.
An electrical signal triggers the parking brake valve.
The parking brake valve position changes, and oil
pressure in the parking brake cylinder is relieved.
The spring pressure automatically applies the brake
if the system loses oil pressure.
FLOW AMPLIFIER, SECTION 5 OF
HYDRAULIC PLATE
The flow amplifier regulates and directs flow of oil
to the steering cylinder. See Figure 3 and Hydraulic
Schematic. The flow amplifier increases oil flow five
times more than pilot input flow from steering con-
trol unit. The rate of oil flow to steering cylinder is di-
rectly proportional to rate of pilot flow from steering
control unit. The flow amplifier receives oil from the,
132.5 cm
3
(8.09 in.
3
), per revolution pump. When
there is no steering demand, the priority valve in the
flow amplifier allows oil to flow from pump to main
control valve. The pressure of hydraulic oil supplied
to amplifier can be checked at check port M7. For fur-
ther information, see the section Steering System
1600 SRM 1109.
Manifold, Section 1 of Hydraulic Plate
GENERAL
All pressure switches, valves, and other associated
items installed on the manifold can be replaced. Be-
fore removal of any part, check that the area is clean
and protected against dirt and fluid contamination.
NOTE:
It is not necessary to remove the manifold to
replace manifold components. Only remove the man-
ifold from the mounting plate when the whole com-
ponent is to be replaced.
WARNING
Never work under a raised carriage or forks.
Lower the carriage or use blocks and chains on
the mast weldments and carriage so that they
cannot move. Verify the moving parts are at-
tached to parts that do not move.
Some parts have compressed springs under
them that can have enough force to cause dam-
age or injury. Always use caution and wear eye
protection when removing parts.
Before removing any hydraulic components or
disconnecting any hydraulic lines, release the
hydraulic pressure from the hydraulic circuit
as follows:
• Shut engine OFF and completely lower car-
riage. Install blocks at wheels to prevent lift
truck from moving.
• Release the accumulator pressure by operat-
ing the brake pedal.
The manifold (see )Figure 2 is an integral part of the
Hydraulic Plate. For more information on the repairs
to all parts of the Hydraulic Plate, see the section
Hydraulic System 1900 SRM 1239.
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