jcb JS70, Service Manual

Page: 160 / 385

Pump inspection
24 - 12
Section E Hydraulics
9803/6020
Section E
24 - 12
Issue 1
Hydraulic Pump
Part(s) Inspection/Measurement Standard Permissible Measuring Corrective Action
Area Value Tolerance Tool
Piston/shoe Lateral wear between 0.05 mm 0.2 mm Dial gauge Replace if wear > 0.2 mm
assembly the piston and shoe (0.002 in) (0.008 in) max (0.008 in)
(see step 2a)
Piston/ Clearance between the 0.035 mm 0.05 mm Micrometer or If excessive wear or
cylinder piston O/D and the (0.0014 in) (0.002 in) max air micrometer surface damage is found,
block cylinder block I/D replace the piston/shoe
(see step 2b) Visual check assembly or the cylinder
block, or both.
Shoe Shoe thickness 4 mm 3.8 mm Slide calipers Replace if shoe thickness
(0.16 in) (0.15 in) is < 3.8 mm (0.15 in)
Shaft Contact area of oil ø 28 mm Wear 0.025 mm Surface rough- Replace if wear > 0.025 mm
seal lip (see step 2c) (1.10 in) (0.001 in) ness meter (0.001 in)
Spline area Visual check Carry out a colour check on
the gear surface, etc.
Replace if any crack is found
or if abnormal wear, damage
etc. is present.
Cylinder Mating sliding surfaces Ra=0.2 mm Ra=0.8 mm Surface rough- If the surface roughness
block/control (0.008 in) (0.03 in) ness tester Ra=0.8 mm (0.03 in) or
more, use a flat surface
lapping machine to reduce
this to Ra=0.8 mm (0.03 in)
or less.
Barrel/spool Clearance between 0.013 mm 0.025 mm Micrometer Replace if clearance is
barrel and spool (0.0005 in) (0.001 in) max and cylinder > 0.025 mm (0.001 in) or if
gauge damage or abnormal wear
prevents smooth operation.
Housing/ Clearance between 0.013 mm 0.025 mm Micrometer Replace if clearance is >
spool housing and spool (0.0005 in) (0.001 in) max and cylinder 0.025 mm (0.001 in) or if
gauge damage or abnormal wear
prevents smooth operation.
Housing/ Clearance between 0.025 mm 0.040 mm Micrometer Replace if clearance is >
spool housing and spool (0.001 in) (0.0016 in) max and cylinder 0.040 mm (0.0016 in) or if
gauge damage or abnormal wear
prevents smooth operation.
Housing/ Clearance between 0.0275 mm 0.040 mm Micrometer Replace if clearance is >
control the housing bore I/D (0.0011 in) (0.0016 in) and cylinder 0.040 mm (0.0016 in) or if
piston and the control piston gauge damage or abnormal wear
O/D prevents smooth operation.
Clean all parts in a suitable solvent and dry using compressed air.
1 Wear Limits Table