Komatsu 930E-2, Shop Manual

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Removal
If the Brake Valve is to be removed from the vehicle
for repair or adjustment, additional equipment will be
required as outlined in disassembly, assembly.
NOTE: Minor repairs and service adjustment may not
require the removal of the brake valve.
Before disconnecting pressure lines, replacing
components in the hydraulic circuits, or installing
test gauges, always bleed down hydraulic steering
and brake accumulators. The steering accumula-
tors can be bled down with engine shut down,
turning the key switch “Off” and waiting 90 sec-
onds. Confirm the steering pressure is released by
turning the steering wheel - No front wheel move-
ment should occur.
Open bleed down valves (6 & 7, Figure 3-1) located
on the brake manifold. This will allow both accu-
mulators for the rear brakes and both accumula-
tors for the front brakes to bleed down.
Before disabling brake circuit, be sure truck
wheels are blocked to prevent possible roll-away.
1. Securely block the wheels to prevent possible
roll-away.
2. Place selector switch in NEUTRAL, turn the rest
switch ON. Turn key switch OFF to shut down
engine and allow 90 seconds for steering system
accumulators to bleed down. Open valves (6 & 7,
Figure 3-1) to bleed down all four brake accumu-
lators.
3. Remove access panel in front of operator’s cab.
4. Tag and remove all hydraulic lines from brake
valve. Plug lines and ports to prevent possible
contamination. Remove all valve fittings except
the fitting at port “PX”. Disconnect wiring harness
at differential pressure switch connector.
5. Disconnect retard pedal harness.
6. In the cab at the brake valve, remove capscrews
and lockwashers securing the brake valve as-
sembly to the mounting structure.
7. Slide brake valve downward and remove from
cab.
8. Move brake valve assembly to a clean work area
for disassembly.
Installation
1. Place the brake valve assembly into position and
secure in place with capscrews and lockwashers.
Tighten capscrews to standard torque.
2. Remove plugs from brake valve assembly and
hydraulic lines. Install fittings and connect lines to
brake valve assembly and tighten. Connect differ-
ential pressure switch to harness.
NOTE: Prior to checking the brake valve operation, the
steering system must have the proper nitrogen pre-
charge in the steering accumulators (refer to Section
L, “Hydraulic System” for steering accumulator pre-
charge procedure). In addition, the brake system lines
must be bled of air and the brake accumulators must
also be precharged with nitrogen (refer to brake accu-
mulator precharge procedures, this section).
3. Connect electronic retard pedal connector to truck
harness.
4. With the engine shut down and key switch OFF,
open both brake accumulator bleed down valves
(6 & 7, Figure 3-1). Precharge both accumulators
mounted on brake manifold (5) to 1400 psi (9.65
MPa).
5. Remove charging kit from brake manifold accu-
mulators and install on external accumulators
located behind right front tire. Precharge both
accumulators to 1400 psi (9.65 MPa).
NOTE: For best performance, charge the accumula-
tors in the temperature conditions the vehicle is ex-
pected to operate in. During the precharge, allow
temperature of the nitrogen gas to come into equilib-
rium with the ambient temperature.
6. Close both accumulator bleed down valves after
all four accumulators have been properly
charged.
7. Start the engine. Partially apply the brakes and
open the supply plug at each wheel to bleed air
from brake lines and brakes. Close supply plug
after bubbles disappear.
8. Check for fluid leaks at the brake valve.
J3-2 Brake Circuit Component Service J03019 1/99