To prevent personal injury, a heavy iron or
steel barred shield, or the equivalent should
be positioned between the operator and
the spring brake when being disassembled
Apply about 11,120 N (2,500 lbs) force on the
unit. Remove clamp band bolt and nuts and
clamp ring (Fig. 6).
Slowly release the shop press until the spring
brake chamber can be separated and the spring
brake diaphragm can be removed (Fig. 7).
If pressure remains between the ram and
the actuator, either the spring brake unit is
not manually released or a failure has
occurred in the release mechanism. If the
unit is released but pressure is present,
continue to relax the press slowly until the
spring is fully extended and all parts fall free
Lift off the head-spring piston subassembly with
care since the power spring is caged between
the piston and head (Fig. 9).
Remove the diaphragm. When the diaphram is
removed, inspect the inside of the flange case,
return spring, pushrod plate, screw and plastic
guide rings. If the condition of these parts are
questionable refer to the text covering
DEFErIVE PUSHROD SEAL.
Position new spring brake diaphragm in the
spring brake head and install both on top of the
flange case. Position the complete assembly in
the press with a slit-tube type adapter between
the press ram and the head of the spring brake
Be sure the parts are lined up and apply 2.668-
3.559 kN (600-800 lbs) force to compress the
return spring between the diaphragm and the
While the assembly is compressed the spring
brake chamber clamp band can now be
assembled. Tap the clap band all the way
around while tightening the clamp band nut to
insure proper seating. Tighten nuts to 27-34
N.m (20-25 ft lbs).
Reinstall the brake chamber assembly and
instructed in the REINSTALL instructions.
REPLACE SPRING BRAKE UNIT OR SERIVICE
Block wheels to prevent vehicle from moving.
Manually release the spring brakes (refer to
MIAL RELEASE OF SPRING BRAKE). After
releasing brakes release the air pressure in the
parking brake system by placingthe
brake control in apply position.
To ease the installation, the service brake
pushrod should be extended. Extending the
pushrod can be accomplished by manually
pushing back the slack adjuster or by application
of the service brakes. While the pushrod is
extended, a locking type pliers should be used to
retain the Pushrod in the extended position (Fig.
10). Then release the service brakes or slack
Remove air hoses from parking brake and
service brake chambers. Tag hoses for proper
identification at reassembly.
CIS-4101W - Page 7