MCi Crusader II 1989 Maintenance Manual page 147

Date
1-1-89 .
Page
4-17
MC-9 MAINTENANCE MANUAL
close the emergency brake air line on the first service brake
application.
For shuttle valve disassembly, refer to figure 4-17.
1
1. Bonnet
2. Retainer
3. Upper Diaphragm
4. Piston
5. Spacer
6. Lower Diaphragm
7. Seat
8. 0-Ring
9.
Body
0
s: from service port
e: from emergency
port brake valve
o: outlet emergency
brake
Figure 4-17. Shuttle Valve Parts.
QUICK RELEASE VALVES
e
The quick-release valves. used for the entrance door and
the park brake systems. are found in the tire compartment
These valves speed up the release of air pressure.
In the parking brake system. when a brake valve application
is released. the exhaust ports of the quick-release valves open
and the air pressure accumulated in the brake chambers is
exhausted through the quick-release valves, rather than
exhausting back through the brake valve.
A line from a delivery port of the brake valve is connected to
the top port of each quick-release valve. The two side ports are
for brake chamber connections and the bottom ports are the
exhaust
OPERATION
When a brake valve application is made, :1ir pressure entgrs
the top port of the quick-release valve. moves the diaphragm
down. closing the exhaust port At the same time this air pres-
sure forces the edges of the diaphragm down and flows past
into the brake chambers.
As soon as the brake chamber pressure beneath the dia-
phragm equals the air pressure being delivered by the brake
valve. the diaphragm spring forces the outer edges of the dia-
phragm against the body seat The exhaust port is still sealed by
the center portion of the diaphragm. When the brake valve is
released. air pressure above the diaphragm is exhausted. Now.
the pressure under the diaphragm raises it and the exhaust port
opens allowing brake chamber pressure to release.
MAINTENANCE
Every year or after 50,000 miles (80,000 km) remove the
quick-release valve. dismantle it and clean all parts. The dia-
phragm should be replaced if worn or deteriorated. See figure
4-18.
SERVICE CHECK
1. Apply the parking brake and note the activation of the
brake chambers served by the quick-release valve.
2. Release the brake and observe ·that the air pressure is
quickly exhausted through the quick-release valve.
3. Make and hold a brake application and check the exhaust
port of the quick-release valve for leakage.
If the q uick-retease valve does notfunction properly or leaks.
excessively, it should be replaced or repaired as outlined
below.
REMOVAL AND INSTALLATION
1. Block the coach by means other than the brakes.
2. Vent the air brake system.
3. Disconnect the air lines from quick-release valve.
4. Remove mounting bolts and valves.
To reinstall, mount quick-release valve with its exhaust port
pointing down. Connect the brake valve to the top port and
brake chamber lines to side port. Make sure exhaust port is not
restricted.
2
1.
Body
2.
Cover
3.
Diaphragm
4. 0-ring
5. Cap
Screw
Figure 4-18. Quick Release Valve.
DISASSEMBLY AND REPAIR
1. Remove the cover using a wrench on the square portion
of the exhaust port Remove diaphragm and 0-ring.
2. Clean all parts in cleaning solvent lnspectthe diaphragm,
especially the lower part that contacts the exhaust seat, for
wear or deterioration.