BRAKES-PARKING MOTOR TRUCK SERVICE MANUAL
tion, use a soft hammer to bump the head carefully to
loosen since head may be stuck in place by foreign
material, sealer, or corrosion. If difficulty in removing
head is still experienced, use the three mill notches
equispaced around the cylinder head for prying head
from cylinder case (Fig. 12). Use a screwdriver or
similar tool carefully at each notch in turn so that cylinder
head does not become cocked.
Fig. 13 Removing Head, Spring and Piston Assembly
When cylinder head is free, slowly release press
gradually and remove cylinder head, spring and piston
assembly from cylinder case (Fig. 13).
Fig. 12 Using Screwdriver to Loosen Cylinder Head
CAUTION: If spring brake unit has a damaged
piston, the spring is no longer restricted when snap ring
is removed. This could allow cylinder head to be
forcefully expelled. When this condition exists or when
there is doubt as to the spring being restricted, always
use a tool similar to a crank shaft gear puller (SE17151).
On early production spring brake cylinder heads
(where no notches were provided) the cylinder head can
be reworked to include these notches. When making
this modification, be careful to avoid cutting through the
cylinder head wall. While there is no air pressure under
the spring brake cylinder head, any notch inadvertently
cut through the head would allow dirt or moisture to enter
and cause damage to internal parts.
It should be further emphasized that the addition of
notches to the cylinder head does not lessen the need
Fig. 14 Loosening Safety Washer.
for the safety precautions previously pointed out. Always
10. In order to dissemble the head, spring and piston
mount spring brake assembly in press when
assembly, this unit must be set under a press.
Use a tool similar to SE17151. Fold a small