SECTION 35 - HYDRAULIC SYSTEM 121
BACKHOE
Refer to the following backhoe fault finding chart after first considering the preceding charts. This chart should
only be referred to if the supply system is operating normally, thereby confirming that the hydraulic supply sys-
tems and the pump are correctly operating. See also “Fault finding hydraulic pump”.
PROBLEM CAUSE CORRECTION
The lifting system is inoperative,
is too slow, loses power or does
not hold
Lifting system relief valve stuck
open, set too low or seat leaking
Valve spool leakage
Piston seals leaking or cylinder
barrel damaged
Test the pressure of the lifting
system relief valve.
Examine lift section of backhoe
control valve assembly for wear and
scoring.
Examine/reseal piston and gland.
The digging control fails to
operate, is slow or loses power
Digging system relief valve
(piston end) stuck open, set too
low or seat leaking
Valve spool leakage
Piston seals leaking or cylinder
barrel damaged
Test the pressure of the digging
system relief valve.
Examine digging section of backhoe
control valve assembly for wear and
scoring.
Examine/reseal piston and gland.
The digging control fails to
operate, is slow or loses power
Bucket circuit relief valve (rod
end) stuck open, set too low, or
seat is leaking
Valve spool leakage
Piston seals leaking or cylinder
barrel damaged
Test the pressure of the bucket relief
valve.
Examine bucket section of backhoe
control valve assembly for wear and
scoring.
Examine/reseal piston and gland.
The telescopic dipper fails to
operate, is slow or loses power
The telescopic dipper system
relief valve (piston end) is stuck
open, set to a too low value or
there is a leak in the seat
Valve spool leakage
Piston seals leaking or cylinder
barrel damaged
Test the pressure of the telescopic
dipper relief valve.
Examine telescopic dipper section of
backhoe control valve assembly for
wear and scoring.
Examine/reseal piston and gland.
Stabilizer pads leaking Stabilizer safety valve leaking
Piston seals leaking or cylinder
barrel damaged
Inspect and overhaul the stabilizer
safety valve.
Examine/reseal piston and gland.
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