4-65. RELAY VALVE REPLACEMENT (Con't).
Coat exhaust port with detergent and water solution. Apply brakes and check for leaks
Release brakes and apply detergent and water solution to exhaust port and check for leaks.
With semitrailer brake system fully charged, close shut-off valve in emergency line tube on towing vehicle.
Disconnect towing vehicle air hose from semitrailer coupling tagged EMERGENCY Coat exhaust port with
detergent and water solution and check for leaks.
Leakage in steps 1 through 3 should not exceed a 1 in. (2.54 cm) bubble in two seconds. If excess leakage is
found, replace relay valve.