4-44. RELAY VALVE MAINTENANCE.
This Task Covers:
l Semitrailer coupled to towing vehicle with airbrake
l Dishwashing compound (Item 6, Appendix E)
system fully charged (para 2-10).
l Marker tags (Item 15, Appendix E)
l Antiselzing tape (Item 16, Appendix E)
General mechanics tool kit
l Two Iockwasher
Personnel Required: Two
Depress and hold brake pedal in towing vehicle
and check to see if brakes apply properly,
Release brake pedal and check to see if air
pressure is released properly.
With semitrailer airbrake system fully charged,
close shut-off valve in emergency line on towing
Disconnect EMERGENCY air coupling (1) and
check to see if semitrailer brakes apply automati-
Connect EMERGENCY air coupling (1) to semi-
trailer and open shut-off valve in emergency line
on towing vehicle. Check to see if semitrailer
brakes release automatically.
b. LEAKAGE TEST
Apply soap and water solution to relay valve cover flanges (3) and fittings (5).
If leakage is detected, tighten nuts (7) on cover flanges (3).
Apply soap and water solution to exhaust port (8). Depress towing vehicle brake pedal and check for leakage.
Apply soap and water solution to exhaust port (8). Release towing vehicle brake pedal and check for leakage.