Komatsu PC88MR-10 Shop Manual page 389

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. Lower the work equipment to the ground with
arm IN operation, and stop the engine.
a Since anti-drop valve is attached to arm
cylinder head side, remaining pressure drops
due to less hydraulic oil on head side of arm
cylinder when work equipment is lowered to
the ground. Also, Remaining oil on head side
is reduced.
2. Release remaining pressure in hydraulic
cylinder circuit
PC88MR-10
30 Testing and adjusting
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 to 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) 4 to 5 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.
With anti-drop valve of arm
(Releasing remaining pressure with maximum arm
OUT posture)
Check function of PPC circuit accumulator
a Stop the machine on a level ground.
1. Hold the work equipment in the maximum reach
posture (arm OUT, bucket DUMP stroke end) at
height (a) from the ground.
a: 1.5 m
2. Keep the work equipment at the maximum reach,
turn the starting switch to OFF position, and stop
the engine.
3. Turn the starting switch to ON position.
Hydraulic system
30-39