Service Manual

120 PW / PY Series
Refer to Figure 13.
Disassembly
1. Tilt the pump on its side, drain remaining oil. Lift
out the cylinder block assembly (38).
2. Remove the pistons, springs and piston seats.
Inspection
1. Inspect the running surface of the cylinder block
and piston ends for damage, nicks or unusual
wear patterns.
The running surface may show evidence of
minor abrasion. This will be normal wear. If
grooved or smeared, replace with a new cylinder
block assembly.
2. Inspect the piston springs for distortion or
breakage. If necessary, replace with a new
cylinder block kit.
3. Inspect the piston seats. Residual oil may
cause these to remain stuck to the inside of the
pistons.
REMOVAL, INSPECTION AND
ASSEMBLY OF THE CYLINDER
BLOCK
Figure 13. PW / PY Pump Cylinder Block
Assembly
1. Install piston seats into the end of the pistons.
2. Install springs into the pistons.
3. Install one at a time, pistons, springs and seats
as one assembly into the cylinder block.
4. With the pump housing tilted on its side, install
the cylinder block assembly (38) with pistons
contacting the thrust bearing.
NOTE: To check that piston placement is
correct, push downward on the cylinder
block assembly (38). If this results in a
spring action the block assembly has
been installed correctly. If this cannot be
accomplished, remove and reassemble
the block assembly. Place a rubber band
around the cylinder block pistons to hold
them in position during installation. Then
after installation cut the rubber band and
remove it. Check for cylinder block as-
sembly for spring action.
38
Spring (7X)
Cylinder Block
Piston
Seat (7X)
Piston (7X)