MCi Crusader II 1989 Maintenance Manual page 154

Date
1-1-89
Page ___
4-_24 _ _ _
MC-9 MAINTENANCE MANUAL
Air pressure enters the pressure side of the brake chamber
against the diaphragm which moves the push rod assembly
forward. The push rod is connected to a slack adjuster which is
attached to a camshaft that rotates the brake cam and applies
the brakes.
When air pressure is released from the brake chamber, the
push rod return spring in combination with the brake shoe
return spring returns the diaphragm, push rod, slack adjuster
and brake cam, releasing the brakes.
Push rod travel should be kept as short as possible without
causing brake drag. Excessive push rod travel shortens dia-
phragm life, gives slow braking response and wastes air.
TESTING
Check push rod-to-slack adjuster alignment in both the
applied and released positions to be sure the push rod moves
out and returns properly and without binding. Also check the
angle formed by the slack adjuster arm and push rod. It should
be 90" or greater when the chamber is in the applied and
released positions.
MAINTENANC.E
Every 50,000 miles (80,000 km) or more often, depending on
the type of operation, disassemble brake chambers and clean
all parts. Install a new diaphragm, or any other rubber parts, if
they are worn or deteriorated. When the diaphragm or spring
are replaced in one brake chamber, they should be replaced in
the corresponding brake chamber on the same axle.
Apply the brakes and check that the brake chamber push
rod moves out promptly without binding. Release the brakes
and note that the push rod returns to the released position
promptly and without binding. Check push rod travel to be sure
it is at a minimum without bra~e drag.
With a full pressure application, check the brake chamber
for leakage. No leakage is permissible.
1.
2.
3.
4.
5.
6.
7.
CAUTION: If leakage is detected around
the flange, or clamping ring, the bolts
should be tightened evenly but only enough
to stop the leakage. Otherwise the dia•
phragm, flange sealing surface or clamping
ling could
be
distorted.
5
Clamp Ring
8.
Spring
Nut
9. Nut
Solt
11.
Push Rod Assy.
Diaphragm
12.
Nut
Pressure Plate 13. Yoke
Plug
14. Lockwasher
Non-Pressure
Plate Assy.
Figure 4•30. Brake Chamber Installed at Trailing Axle.
REMOVAL AND INSTALLATION
1. Block the coach by means other than the brakes.
2. Disconnect the air line and push rod yoke. Refer to figure
4-30.
3. Remove brake chamber.
4. For installation, mount brake chamber to mounting
bracket.
5. Install yoke and its lock nut on push rod and connect to
slack adjuster arm. •
Check the angle formed by the push rod and slacJ< adjuster.
The angle should never be less than 90° when full air pressure
is applied to the brake chamber when the brakes are cold and
properly adjusted.
DISASSEMBLY AND REPAIR
After cleaning the exterior of the brake chamber. matchmark
the parts in such a way that they can be assembled the same
way.
7
-~t•12
';_~
11
\ c:- ,
13
_.,,
..~@n;- :.
-:§
Figure 4•29. Front and Trailing Axle Brake Chambers.