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D10-991-2400 5/1/04
D/G-10 Service (Hydraulic End)
1. Remove Pump Housing
a. Remove the head of the pump, and the diaphragms, as
outlined in the Fluid-End Service Section.
b. Drain the oil from the pump housing by removing the drain
plug (34).
c. Set the hydraulic end of the pump face-down on the cylinder
housing (24), onto a smooth, clean surface.
d. Check the shaft for sharp burrs. Smooth any burrs, to prevent
scarring the housing seals (64) when you disassemble the
pump.
e. Remove the bolts (29; 25 or 44) that secure the housing to
the cylinder casting. The piston return springs (50) will force
the cylinder housing and housing apart.
NOTE: When reassembling later, note that one bolt (29)
is 1/4" (5 mm) longer than the other (25 or 44). The
longer bolt must be installed in the 10 o’clock position
of the cylinder housing (24).
f.
Lift off the housing (30).
g. Inspect the cam and bearings (62), and the bearing race in
the rear of the housing. If the bearings are pitted or binding,
or if the housing race is worn, replace them both.
NOTE: The numbers in parentheses are the Reference
Numbers on the exploded view illustrations found in this
manual and also in the Parts Manual.
CAUTION: Do not disassemble the hydraulic end of the
pump unless you are a skilled mechanic. For assistance,
contact Wanner Engineering (TEL 612-332-5681 or FAX 612-
332-6937) or the distributor in your area.
CAUTION: The two bolts (29; 25 or 44) that screw through
the back of the housing into the cylinder housing (24) hold
the housing to the pump housing. Do not remove them
except when repairing the hydraulic end.
NOTE: The following service procedures refer several times
to the Wanner Tool Kit (P/N A03-175-1101). We strongly urge
you not to try to repair the hydraulic end of the pump
without using the tools in this kit (available from Wanner
or your local distributor).
2. Disassemble Pistons
a. With the pump housing removed (see above), turn the unit
over and set it on a flat surface, piston side down.
b. With the diaphragms removed (see the Fluid-End Service
Section), reinsert a follower screw (17) into the hole in one
of the valve plungers (54). Tap the screw lightly with a
hammer; the plunger (21) should slip off the valve plunger
(54).
The hydraulic piston assembly (50-59) can now be
disassembled. Inspect all parts, and replace all O-rings and
any other parts that are worn or damaged.
c. Repeat step b for the remaining pistons.
NOTE: When you reassemble the hydraulic piston, use
new plungers (21). They are press-fit onto the valve
plungers (54) and are not reusable.
3. Reassemble Pistons
a. Drop a ball (58) into each opening in the bottom of a piston
assembly (59).
b. Insert a retaining washer (57) and O-ring (56) to hold the
balls in place.
c. Insert a valve plunger (54) into a valve cylinder (55). Slide a
spring (53) over the plunger, inside the valve cylinder.
d. Insert an O-ring (52) into a spring retainer (51).
e. Slide the assembled valve cylinder, plunger, and spring (53-
55) into the spring retainer (51).
f.
Slide the complete cylinder-and-retainer assembly (51-55)
into the piston assembly (59).
g. Insert a return spring (50) into the piston assembly, wide
end first. This is a tight fit, and can best be done by “screwing”
the spring in counterclockwise.
h. Repeat the above procedure for the other two pistons.
4. Reassemble Pump Housing
and Cylinder Housing
NOTE: Inspect the shaft seals (64) before continuing. If
they look damaged in any way, replace them (remove by
pounding them out from inside the pump housing). Both
seals should be replaced at the same time. Clean the bore
in the housing using emery cloth or ScotchBrite™.
a. Place the cylinder housing (24) face-down on a flat surface.
b. Insert the assembled pistons (50-59) into the cylinder
housing. The holes on the foot end of the pistons should all
point toward the center of the casting.
c. Note the location of the outer ring of holes in the cylinder
housing and in the pump housing flange (in particular, the
holes where bolts 29 and 25 or 44 will be installed).
d. Stand the camshaft assembly (62) on the cylinder housing
(24).
CAUTION: The pilot bearing MUST be properly nested
in the bearing race during assembly. If misaligned, the
bearing will be damaged and the pump will fail within
the first hours of operation.
