4-38. UNLOADER VALVE - REPLACE.
This Task Covers:
Tool Kit, General Mechanic's: Automotive (Appendix B, Section III, Item 1).
Teflon Tape (Appendix E, Section II, Item 7).
Engine shut down and cool.
Enclosure Removed (para. 4-13).
a. Removal. (Refer to Figure 4-29).
Compressed air can be dangerous if not used properly, It can cause severe
injury or death. DO NOT disconnect hose assembly or components before first
relieving the air-receiver tank of all pressure.
Open condensate drain valve on reel cabinet to relieve tank pressure.
Verify that pressure has been relieved by reading the air pressure gauge. It should read zero.
Disconnect braided hose assembly (1), braided hose assembly (2), nylon tube (3) from unloader valve (4).
Braided hose assembly (2) must be disconnected from both ends.
Remove unloader valve (4) and nipple (5) from tank assembly (6).
Remove nipple (5), swivel adapter (7), push-in fitting elbow (8) from unloader valve (4).
Clean threads of the following fittings and tape: nipple (5), swivel adapter (7), push-in fitting elbow (8), and fitting
on hose assembly (2).
Install nipple (5), swivel adapter (7), push-in fitting elbow (8) into unloader valve (4).
Install nipple (5) and unloader valve (4) into tank assembly (6).
Connect braided hose assemblies (1 and 2), nylon tube (3) to unloader valve (4).
To check correct operation of the unloader valve, check air pressure gauge (9) and control panel (10) to see when
the engine kicks in and when it idles down.
The cut-in pressure should be about 145 psi, the cut-out pressure should be about 175 psi.