42–06 Brake Chamber
Inspection (All Models)
DANGER
Do not loosen or remove the parking brake clamp
ring for any purpose at any time. The
parking/emergency brake section is not intended
to be serviced. Serious injury or death may result
from sudden release of the power spring.
Before doing any repairs or adjustments on a
service/parking brake chamber, read the appli-
cable warnings and instructions in the applicable
brake chamber section in Group 42 of the
Cargo
Workshop Manual
.
WARNING
Do not operate the vehicle with the front brakes
backed off or disconnected. Backing off or discon-
necting the front brakes will not improve vehicle
handling and may lead to loss of vehicle control
resulting in property damage or personal injury.
NOTE: Vehicles operating under severe or ad-
verse conditions should be checked more fre-
quently. If the brake chamber requires disas-
sembly, see Group 42 of the
Cargo Workshop
Manual for instructions.
1.
With the slack adjuster properly adjusted, check
the angle formed by the centerline of the piston
rod and slack adjuster. This angle should be
greater than 90 degrees in the released position
and approach 90 degrees in the applied position.
See
Fig. 1
.
At angles less than 90 degrees, brake chamber
force is reduced, which reduces braking
efficiency.
2.
Check each brake chamber for correct installa-
tion.
2.1
Check each mounting stud for the pres-
ence of prevailing torque locknuts and
hardened flatwashers. Make sure that the
hardened flatwashers are installed be-
tween the mounting bracket and the lock-
nuts. Do not install flatwashers touching
the service (non-pressure) chamber.
2.2
If the locknuts are loose, tighten them.
For correct torque values, see the appli-
cable brake chamber section in Group 42
of the
Cargo Workshop Manual
.
3.
Observe the piston rod engagement with the cle-
vis. Engagement of at least 7 threads is required;
there should be 1 inch (25 mm) clearance from
the centerline of the clevis pin hole to the end of
the piston rod. See
Fig. 2
. Adjust if needed.
4.
Check the tightness of the piston rod nut. Tighten
if needed.
5.
See if the chamber piston rod is in line with the
slack adjuster. Misalignment can cause the pis-
ton rod to rub on the non-pressure chamber and
cause a dragging brake. Reposition the brake
chamber on the mounting bracket, if necessary.
6.
Inspect the condition of the hose(s) to the brake
chamber. Check carefully for chafing, restrictions
such as kinking or bending, and make sure the
hoses are properly supported. Replace a dam-
aged hose with the same size hose. With the
service brakes applied, check for leaks at the
hose-to-chamber connections. Any leaks are
probably caused by loose connections or by a
damaged hose fitting. Eliminate all leaks.
On chambers equipped with an external breather
tube, make sure that the flexible elbows are in
place and that the connector tube is inserted into
each elbow 1/2 inch (13 mm).
f420009a
07/27/94
1
3
2
C
B
A
A. Brakes Released
B. Brakes Applied
C. Greater than 90
degree angle
1.
Brake Chamber
2.
Piston Rod
3.
Slack Adjuster
Fig. 1, Angle Between Piston Rod and Slack Adjuster
Brakes
42
Cargo Maintenance Manual, January 2000
42/2