Komatsu PC88MR-10 Shop Manual page 390

30 Testing and adjusting
Hydraulic system
4. Set the work equipment lock lever in FREE
position.
5. Check that the work equipment is lowered to the
ground by slowly operating the work equipment
control lever to the boom LOWER direction fully
to the stroke end.
a If the work equipment is lowered down under
its weight to the ground, the accumulator is
normal.
a Pressure of accumulator drops gradually
after stopping the engine. Be sure to perform
this work (procedure 2 and 3) in 15 seconds
after stopping the engine.
a If the work equipment is not lowered or stops
on the way lowering, pressure in the
accumulator may be dropped. Pressure
cannot be released with this procedure if the
function of accumulator is deteriorated.
a Accumulator is a periodic inspection item and
an important periodic replacement part.
Releasing remaining pressure from cylinder
1. Operate the arm to the maximum arm OUT side,
lower the work equipment to the ground, and
stop the engine.
a Since anti-drop valve is attached to arm
cylinder head side, remaining pressure
increases due to more hydraulic oil applied to
head side when work equipment is lowered
to the ground. If it is the case, perform more
times of releasing of the remaining pressure
from hydraulic piping.
30-40
2. Release remaining pressure in hydraulic
cylinder circuit
1) Turn the starting switch to ON position and
set the work equipment lock lever to FREE
position, and then operate the right and left
work equipment control levers forward and
backward, and to the right and left.
a The control valve is operated by the
pressure in the accumulator. But the
pressure in the accumulator is used up
after the work equipment control levers
are operated 2 or 3 times.
2) Start the engine and run it at low idle for 5
seconds to increase the pressure in the
accumulator.
a The engine does not start unless the work
equipment lock lever is set to LOCK position.
3. Repeat above procedure 1) and 2) 10 to 15
times, and all remaining pressure is released
from the cylinders completely.
4. Loosen oil filler cap of the hydraulic tank
gradually to release the air in the tank.
a Leave the oil filler cap of the hydraulic tank
removed.
a When disassembling the anti-drop valve,
perform releasing remaining pressure in
cylinders, loosen anti-drop valve assembly
mounting bolts gradually. Check that
hydraulic oil pressure is released, remove it
as an assembly, and disassemble it.
Releasing remaining pressure from swing motor
circuit
a The remaining pressure in the swing motor
circuit can be released by performing the same
operation as that described in preceding
"Releasing remaining pressure in hydraulic
cylinder circuit" (Operate the lever to SWING
only, however).
Releasing remaining pressure from travel motor
circuit
PC88MR-10