JLG 1850SJ Service And Maintenance Manual page 406

SECTION 5 - BASIC HYDRAULIC INFORMATION & HYDRAULIC SCHEMATICS
SWASHPLATE
Carefully inspect each surface of the swashplate for wear. All
swashplate surfaces should be smooth. Inspect the swash-
plate's slipper running surface for damage and brass transfer.
Excessive brass transfer from slippers may indicate that the
slippers should be replaced. Finally, check the swashplate
bearing journal for scratches. Replace swashplate if necessary.
B040
JOURNAL BEARINGS
Inspect the journal bearings for damage or excessive wear.
Replace journal bearings if scratched, warped, or excessively
worn. The polymer wear layer must be smooth and intact.
VALVE PLATE
Inspect the valve plate for scratches and grooves. Check the
plate for evidence of any cavitation along the running face of
the valve plate. If pitting from cavitation exists, replace the
valve plate. Check for excess wear on the brass running face. If
any discoloration or burn marks are observed, replace the
valve plate.
Run a fingernail or pencil tip across the diameter of the sealing
land surface (see illustration). No deep or outstanding grooves
should be felt, as these may decrease pump flow. Lap or
replace if grooves or nicks are present. Inspect the mating sur-
faces of the endcap and valve plate for any possible contami-
nation; even a few thousandths of an inch may affect pump
operation.
Measure the thickness of the valve plate. Ensure that valve
plate parallelism is equal to or less than 0.025 mm [0.001 in].
Appearance should be flat and smooth on both the running
face and the bottom surface. The valve plate should be flat to
0.005 mm [0.0002.in] convex. A magnetic particle inspection is
5-154
recommended to detect cracks. The valve plate must be
replaced if any cracks exist.
ENDCAP
Inspect the endcap. Remove the check valve (B092) to expose
the spring (B091). Check and record orientation of the timing
pin (J050) The split in the timing pin should be facing into or
out of the slot in the valve plate. Inspect the check valve for
wear on its sealing face and replace if necessary. Make sure the
spring is undamaged. Replace any components if excess wear
B030 is present.
SERVO PISTON
Check the servo piston assembly (P020) for any obvious wear
or damage. Check the corresponding endcap bore for galling
or excessive wear. Discard the piston if damaged. Replace the
servo piston-rings.
B090
J050
B091
B092
P020
3.88 mm [0.153 in] min.
0.025 mm
[0.001 in]
0.005 mm
[0.0002 in]
convex ma x
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