AIR RELAY VALVE REPLACEMENT.
This task covers:
Tools and Special Tools
Tool Kit, General Mechanics: Automotive
Wheels Chocked (page 2-17)
Tags, Identification (item 22, appendix E)
Tape, Teflon (item 23, appendix E)
Loosen draincock (1) and drain air from air tank (2).
Tighten draincock (1) after air has been drained.