245
Air System
2
9
4
3
7
8
6
5
Figure 6-44, PP-1 Components
Parking Brake Control Valve (Bendix PP-)
The parking brake control valve is a Bendix PP-1 manually operable on-off air control valve with an ex-
haust function. Refer to the “Spring Brake Valve- Bendix SR-1" section of this chapter for a description
of parking brake air system operation.
PP- Preventive Maintenance
Every 50,000 miles, 6 months, or 1,800 operating hours, rebuild the
PP-1.
PP- Removal
Block and/or hold the vehicle by a means other than air brakes and
drain all air tanks to zero psi. Callouts refer to the numbers in Figure
6-
44
,
1. Drive the button roll-pin (1) out with a punch and remove the
button.
2. Unplumb the air connections, remove the panel mounting nut
(2), and remove the valve.
PP- Installation
1. Install valve in panel, securing with the panel mounting nut.
2. Reconnect the air lines.
3. Install the operating button. Secure with the roll pin (1).
PP- Disassembly
1. Remove the two capscrews (3) which retain the lower cover and remove the cover. Remove the
sealing ring (4).
2. Insert a small punch through the roll pin hole in the stem and remove the locknut (5) with a 7/16"
wrench.
3. Remove inlet/exhaust valve (6), plunger (7) and spring (8) (if any).
4. Remove O-ring (9) from plunger.
PP- Operating and Leakage Test
1. Connect a 120 psi air source to the supply port. An accurate test gauge should be tee’d into the
supply line and a means of controlling the supply pressure provided. A small volume with a
gauge should be connected to the delivery port.
2. With 120 psi supply pressure, the knob pulled up (exhaust position), leakage at the exhaust port
or the plunger stem should not exceed a 1" soap bubble in 5 seconds. There should be no leakage
between the upper and lower body.
3. Push the knob in (applied position). Leakage at the exhaust port or the plunger should not exceed
a 1" bubble in 3 seconds.
4. Reduce the supply pressure. At a pressure of 40 psi, the button should pop up automatically.
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...