SUB-SECTION 4D
CONTROL VALVES
Figure 4D-3. Control Valve Operation (36Z725)
TABLE 4D-2
TROUBLE, CAUSE AND REMEDY CHART
TROUBLE
PROBABLE CAUSE
REMEDY
Oil leaks at either end of spool.
Defective O-rings in valve body.
Replace O-rings.
Spring-centered spools do not
Broken springs.
Replace springs.
return to neutral.
Foreign particles.
Clean system and valve.
Misalignment of operating linkage.
Check linkage for binding condition.
No motion, slow or jerky action of
Relief valve not properly set, or
Repair, clean and readjust.
hydraulic system.
stuck in base and/or worn.
Dirt or foreign particles lodged
Disassemble, clean and reassemble.
between relief valve control pop
pet and seat.
Spool not moved to full stroke.
Check travel.
No relief valve action (High
Small particle of dirt plugging
Remove relief valve and check
Pressure).
orifice in relief valve sub-
hole. If blocked, deer hole.
assembly.
4D-4