99
Air System
Performance Testing
Test the vehicle air system as follows:
1. Bleed the vehicle air system reservoir gauges down (apply brakes several times) to approximate-
ly 85 psig.
2. With the engine running at full governed speed (no load, no air accessories being used), the com-
pressor should reach governor cut-out pressure (130 psi), then unload.
If the compressor does not reach governor cut-out pressure, check for air leaks in the system. If
reservoir volume and engine RPM are per original vehicle manufacturer’s specifications, system
plumbing leakage must be checked and, if necessary, repaired. See air system leakage test proce
-
dures which follow.
If the compressor fails to unload, verify proper governor operation.
Air System Leakage Test
1. Park your bus on a level surface. Leave engine on.
2. Chock the wheels to prevent movement, then release the parking brake.
3. Build up air tank pressure to governor cut-out pressure (130 psi).
4. Turn engine off.
5. Let air pressure gauges stabilize for 1 minute. After 1 minute, time the pressure drop rate on the
gauges.
Pressure should not drop more than 2 psi per minute with the service brakes released.
Pressure should not drop more than 3 psi per minute with a 90 psi service application.
If pressure drop is excessive, make the necessary repairs.
Listen for air leaks. Soapy water or high frequency acoustic detectors may be used to detect air
leaks.
Summary of Contents for LOW FLOOR
Page 18: ...Specifications 18...
Page 58: ...Preventive Maintenance 58...
Page 110: ...Engine 110...
Page 138: ...Transmission Driveline Rear Axle 138...
Page 182: ...Suspension 182...
Page 260: ...Air System 260...
Page 420: ...Electrical System 420 Deutsch DT Series Connectors...
Page 421: ...Electrical System 421...
Page 422: ...Electrical System 422 Deutsch HD 10 Series Connectors...
Page 423: ...Electrical System 423...
Page 424: ...Electrical System 424 Deutsch HD 30 Series Connectors...
Page 425: ...Electrical System 425...
Page 442: ...Heating Air Conditioning 442...
Page 492: ...Body and Interior 492 Figure 11 33 USSC Seat Assembly...
Page 493: ...Body and Interior 493 Figure 11 34 USSC Seat Suspension Assembly...
Page 495: ...Body and Interior 495 Figure 11 37 Seat Air Connections...