Clean seal groove. Lubricate the groove and
the new seal with an IH 251H EP grease or
equivalent to NLCI #2 multi purpose lithium
grease. Install the new seal. Be sure the seal
is seated, by running your finger around the seal
inside diameter and press seal in place.
Position a new guide ring on each side of the
seal (Fig. 13). The wider flange side will be
away from the seal. Align the skive cuts
approximately 1800 apart.
Install smaller pushrod plate on pushrod if it was
removed. Be sure to thoroughly clean screw
threads and threaded holes in the pushrod.
Apply Loctite General Purpose Lock N Seal to
the screw threads. Install screw to secure small
plate in place. Tighten screw to 20 N.m (15 ft
Apply a small amount of lubricant to tip of
pushrod and insert the pushrod through the seal
from the service brake chamber side of case.
Position return spring in case and compress
spring with large pushrod plate so that the screw
can be threaded in the pushrod. Use General
Purpose Lock N Seal on the screw. Tighten
this screw to 20 N.m (15 ft lbs). The large
pushrod plate must be toward the spring brake
side of unit. The screws can be tightened using
one screwdriver in a vise to hold one screw and
tighten the opposite screw (refer to step 2).
Check the alignment of return spring in case
and to large pushrod plate. Straight alignment
is important for positive rod sealing.
damaged or more than a year old.
To complete the reassembly of the unit refer to
REPLACE SPRING BRAKE UNIT OR SERVICE
BRAKE DIAPHRA(G and complete steps 9, 10
and 11. Then complete steps 10, 11, 12 and 13
of REPLACE SPRING BRAKE DIAPHRAGM.
SERVICE SPRING BRAKE UNIT WITH SUSPECTED
Do not attempt to disassemble power spring
unit while it is on the vehicle; even though
a broken power spring is confirmed, it is
important to manually release the spring
brake unit before any disassembly is per-
formed. Accidental release of the power
spring will cause spring brake components
to be hurled with force which could strike
persons in area causing serious personal
RELEASE OF SPRING BRAKE.
Refer to text REPLACE SPRING BRAKE DIA-
PHRACM. Pay special attention to the
CAURION references. Perform steps 1 thru and
including 7 to remove spring brake head
Use a 3.175 mmn (1/8") diameter punch.
Support the release bolt and knock out lock pin
in release bolt as illustrated in Fig. 15. Then
remove the slotted release nut.
Use a screwdriver to pop off the piston plug in
the center of the piston (Fig. 16).
Insert head-spring piston subassembly in press
(Fig. 17). It is important to position one 356-
381 mn (4-5") diameter slit-tube under the
assembly supporting the piston and another one
over the assembly between the head and the flat
plate under the press ram. Without these tubes,
accomplished. After the ram touches the plate,
the ram must be able to travel a minimum of 203
mm (8") away from the assembly. Without the
length of travel available the spring will not
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