MCi Crusader II 1989 Maintenance Manual page 148

Date
1-1-89
Page · __
4_-1_a _ _
MC-9 MAINTENANCE MANUAL
3. Check the exhaust seat for pitting or nicks. This seat
should be smooth and sharp. If not, use a fine piece of emery.
cloth to restore its finish. Clean or replace as necessary.
To reassemble. position diaphragm and O-ring in place.
Install cover and tighten securely.
R·12 REAR BRAKE RELAY VALVE
The R-12 brake relay valve ls mounted on the center of the
rear baggage compartment bulkhead. Application and release
of the drive axle (and trailing axle) brakes are made through the
relay valve. Lines from. the dry air tank are connected directly to
the valve providing high pressure air close to the drive axle (and
trailing axle) brake chambers at all times. The relay valve is
connected to the brake application valve (located in front tire
compartment) by an air line which delivers air pressure to the
relay valve. The relay valve provides a rapid application of the
drive and trailing axle brakes and acts as a quick-release valve
permitting rapid release of air pressure from the rear brake
chambers.
MAINTENANCE
Every 20,000 miles (32,000 km) check the relay valve for .
proper operation and leakage. If valve leakage occurs, disas-
semble the 11alve. clean and inspect all parts. Refer to figure
4-19. Install new rubber parts and replace any other part found
worn or damaged.
SERVICE CHECK
1. Apply the parking brake push-pull control valve by pulling
up on plunger.
2. Coat the relay valve exhaust port with a soap solution to
check for inlet valve and O-ring leakage.
3. Push to release the parking brake control valve and again
check at the exhaust port for leakage of the exhaust valve.
4. Apply soap solution around the valve where the cover
joins the body to check for seal ring leakage. With the parking
brake in "release" position, apply soap solution to the quick-
COVER
release exhaust port to check the diaphragm exhaust seat.
If the relay valve does not function properly, or if leakage is
excessive, the valve must be disassembled and repaired.
REMOVAL AND DISASSEMBLY
1. Block the coach by means other than the brakes.
2. Vent the air brake system.
3. Tag the lines to aid in reconnection, then disconnect and
remove all air lines.
4. Remove the relay valve from the coach.
NOTE: Prior to disassembly, matchmartt
the location of the mounting bracket to the
cover and the cover to the body.
5. Remove the four capscrews and lockwashers securing
the cover to the body.
6. Remove the cover, sealing ring, and mounting bracket.
7. Remove the piston and O-ring from the body.
8. While depressing the exhaust cover, remove the retaining
ring and slowly relax the spring beneath the exhaust cover.
9. Remove the exhaust cover assembly and O-rings.
10. Remove the inlet/ exhaust valve return spring from the
body.
11. Remove the inlet/ exhaust valve from the body.
12. Remove the valve retainer from the inlet/exhaust valve.
CLEANING AND INSPECTION
1. Wash all parts in mineral spirits: dry all rubbe_r parts.
2. Inspect all parts for signs of wear and/or deterioration.
Inspect springs for cracks, distortion or corrosion.
3. Inspect inlet seat and exhaust seat for nicks and burrs and
r~place as necessary. All rubber parts and any part showing
signs of wear or deterioration should be replaced.
SERVICE .PORT
0-RING
PISTON---tt,,""'---11
SEALING RING
BODY
0-BING
VALVE RETAINER
l(!-:;lr-rt--l-l...-
INLET EXHAUST
VALVE
RETAINING RING
EXHAUST COVER
DELIVERY PORT
SUPPLY PORT
Figure 4-19. Rear Brake Relay Valve R-12.