Air Compressor Unloader and Valve Assembly (012-013)
B3.9 and B5.9 Series Engines
Section 12 - Compressed Air System - Group 12
NOTE: If the compressor has a flat-hat-type unloader cap
(1), it must use an unloader spring and valve seat different
from that used with the three-prong unloader.
Holset SS, E-Type, and ST Models
Assemble the air compressor.
Grease rectangular ring seal, unloader cap, and
unloader body bore with high-temperature grease
(Accrolube lubrication TeflonTM grease, or equiva-
Operate the engine, and check the compressor for air
Install the new rectangular V-seal into the unloader body.
NOTE: The seal must be installed with the grooved side up.
Liberally lubricate the unloader valve bore above and be-
low the rectangular ring seal with high-temperature grease
(Accrolube lubrication TeflonTM grease, or equivalent).
Install a new o-ring seal on the unloader valve body.