SUB-SECTION 4D
CONTROL VALVES
TABLE 4D-6
TROUBLE, CAUSE AND REMEDY CHART
TROUBLE
PROBABLE CAUSE
REMEDY
Defective O-rings in valve body.
Replace O-rings.
Oil teaks at either end of spool.
Replace springs.
Spring-centered spools do not
Broken springs.
return to neutral.
Clean system and valve.
Foreign particle.
Check linkage for binding condition.
Misalignment of operating linkage.
Repair, clean and readjust.
Relief valve not properly set, or
No motion, slow or jerky action of
stuck in base and/or worn.
hydraulic system.
Disassemble, clean and reassemble.
Dirt or foreign particles lodged
between relief valve control pop-
pet and seat.
Check travel.
Spool not moved to full stroke.
Remove relief valve and check
Small particle of dirt plugging
No relief valve action (High
hole. If blocked, clear hole.
orifice in relief valve sub-
Pressure).
assembly.
Replace valve.
Load will not hold.
Oil by-passing between spool
and body.
Oil by-passing piston in cylinder.
Repair or replace cylinder.
Refer to above spool remedies.
Spool not centered.
Disassemble, clean and reassemble.
Load drops when spool is moved
Dirt or foreign particles lodged
from neutral to a power position.
between check valve poppet and
sort.
Replace poppet.
Scored or sticking check valve
poppet.
Figure 4D-12. Control Valve (36Q70)
4D-16
