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9
Repair Instructions P420/P420-0011/P420-0021/P422/P423 and P425
Note: Always take time to lubricate all metal and nonmetal parts with a light film of oil before reassembly. This step will ensure
proper fit, at the same time protecting the pump nonmetal parts (i.e., the elastomers) from cutting and scoring.
1) With a socket wrench,
remove the three discharge
valve plugs and three inlet
valve plugs (32). Inspect
the o-ring (33) for wear and
replace if damaged.
2) Using needle nose pliers,
remove the inlet and dis-
charge valve assemblies
(27A). Note: It may become
neccesary to remove the
valve seat (27) from the
valve casing using a
slidehammer.
3) By inserting a small screw
driver between the valve seat
(27) and the valve spring re-
tainer (30), the valve assem-
bly can be separated.
4) Remove the o-ring (31).
Inspect all parts for wear and
replace as necessary. Apply
one drop of loctite 243 to the
valve plugs (32) and tighten
to 107 ft.-lbs. (145 NM).
5) Use a 8mm allen wrench to
remove the 8 socket head
cap screws (34). Carefully
slide the valve casing (26)
out over the plungers.
6) Remove seal adaptors (20)
and weep return rings (25)
from the valve casing.
7) Remove the pressure rings
(24) and v-sleeves (23 -
Note: P422 & P423 pumps
have a support ring) from
the valve casing (26).
8) Remove the weep grooved
seal (23 or 23B) together
with pressure ring (24 _
P420 and P425 only) out
of the seal adaptor (20).
Check O-rings (21).
IMPORTANT! The grooved
seal (23) on the high-pressure
side is to be fitted carefully
into the valve casing (26)
using a screwdriver. Under no
circumstances must the seal
surface in the valve casing or
the seal lip be damaged.